WordPress/wp-includes/wp-db.php

<?php
/**
 * WordPress DB Class
 *
 * Original code from {@link http://php.justinvincent.com Justin Vincent (justin@visunet.ie)}
 *
 * @package WordPress
 * @subpackage Database
 * @since 0.71
 */

/**
 * @since 0.71
 */
define( 'EZSQL_VERSION', 'WP1.25' );

/**
 * @since 0.71
 */
define( 'OBJECT', 'OBJECT', true );

/**
 * @since 2.5.0
 */
define( 'OBJECT_K', 'OBJECT_K' );

/**
 * @since 0.71
 */
define( 'ARRAY_A', 'ARRAY_A' );

/**
 * @since 0.71
 */
define( 'ARRAY_N', 'ARRAY_N' );

/**
 * WordPress Database Access Abstraction Object
 *
 * It is possible to replace this class with your own
 * by setting the $wpdb global variable in wp-content/db.php
 * file to your class. The wpdb class will still be included,
 * so you can extend it or simply use your own.
 *
 * @link http://codex.wordpress.org/Function_Reference/wpdb_Class
 *
 * @package WordPress
 * @subpackage Database
 * @since 0.71
 */
class wpdb {

	/**
	 * Whether to show SQL/DB errors
	 *
	 * @since 0.71
	 * @access private
	 * @var bool
	 */
	var $show_errors = false;

	/**
	 * Whether to suppress errors during the DB bootstrapping.
	 *
	 * @access private
	 * @since 2.5.0
	 * @var bool
	 */
	var $suppress_errors = false;

	/**
	 * The last error during query.
	 *
	 * @since 2.5.0
	 * @var string
	 */
	var $last_error = '';

	/**
	 * Amount of queries made
	 *
	 * @since 1.2.0
	 * @access private
	 * @var int
	 */
	var $num_queries = 0;

	/**
	 * Count of rows returned by previous query
	 *
	 * @since 0.71
	 * @access private
	 * @var int
	 */
	var $num_rows = 0;

	/**
	 * Count of affected rows by previous query
	 *
	 * @since 0.71
	 * @access private
	 * @var int
	 */
	var $rows_affected = 0;

	/**
	 * The ID generated for an AUTO_INCREMENT column by the previous query (usually INSERT).
	 *
	 * @since 0.71
	 * @access public
	 * @var int
	 */
	var $insert_id = 0;

	/**
	 * Last query made
	 *
	 * @since 0.71
	 * @access private
	 * @var array
	 */
	var $last_query;

	/**
	 * Results of the last query made
	 *
	 * @since 0.71
	 * @access private
	 * @var array|null
	 */
	var $last_result;

	/**
	 * MySQL result, which is either a resource or boolean.
	 *
	 * @since 0.71
	 * @access protected
	 * @var mixed
	 */
	protected $result;

	/**
	 * Cached column info, for sanity checking data before inserting
	 *
	 * @since 4.2.0
	 * @access protected
	 * @var array
	 */
	protected $col_meta = array();

	/**
	 * Calculated character sets on tables
	 *
	 * @since 4.2.0
	 * @access protected
	 * @var array
	 */
	protected $table_charset = array();

	/**
	 * Whether text fields in the current query need to be sanity checked.
	 *
	 * @since 4.2.0
	 * @access protected
	 * @var bool
	 */
	protected $check_current_query = true;

	/**
	 * Flag to ensure we don't run into recursion problems when checking the collation.
	 *
	 * @since 4.2.0
	 * @access private
	 * @see wpdb::check_safe_collation()
	 * @var boolean
	 */
	private $checking_collation = false;

	/**
	 * Saved info on the table column
	 *
	 * @since 0.71
	 * @access protected
	 * @var array
	 */
	protected $col_info;

	/**
	 * Saved queries that were executed
	 *
	 * @since 1.5.0
	 * @access private
	 * @var array
	 */
	var $queries;

	/**
	 * WordPress table prefix
	 *
	 * You can set this to have multiple WordPress installations
	 * in a single database. The second reason is for possible
	 * security precautions.
	 *
	 * @since 2.5.0
	 * @access private
	 * @var string
	 */
	var $prefix = '';

	/**
	 * Whether the database queries are ready to start executing.
	 *
	 * @since 2.3.2
	 * @access private
	 * @var bool
	 */
	var $ready = false;

	/**
	 * {@internal Missing Description}}
	 *
	 * @since 3.0.0
	 * @access public
	 * @var int
	 */
	var $blogid = 0;

	/**
	 * {@internal Missing Description}}
	 *
	 * @since 3.0.0
	 * @access public
	 * @var int
	 */
	var $siteid = 0;

	/**
	 * List of WordPress per-blog tables
	 *
	 * @since 2.5.0
	 * @access private
	 * @see wpdb::tables()
	 * @var array
	 */
	var $tables = array( 'posts', 'comments', 'links', 'options', 'postmeta',
		'terms', 'term_taxonomy', 'term_relationships', 'commentmeta' );

	/**
	 * List of deprecated WordPress tables
	 *
	 * categories, post2cat, and link2cat were deprecated in 2.3.0, db version 5539
	 *
	 * @since 2.9.0
	 * @access private
	 * @see wpdb::tables()
	 * @var array
	 */
	var $old_tables = array( 'categories', 'post2cat', 'link2cat' );

	/**
	 * List of WordPress global tables
	 *
	 * @since 3.0.0
	 * @access private
	 * @see wpdb::tables()
	 * @var array
	 */
	var $global_tables = array( 'users', 'usermeta' );

	/**
	 * List of Multisite global tables
	 *
	 * @since 3.0.0
	 * @access private
	 * @see wpdb::tables()
	 * @var array
	 */
	var $ms_global_tables = array( 'blogs', 'signups', 'site', 'sitemeta',
		'sitecategories', 'registration_log', 'blog_versions' );

	/**
	 * WordPress Comments table
	 *
	 * @since 1.5.0
	 * @access public
	 * @var string
	 */
	var $comments;

	/**
	 * WordPress Comment Metadata table
	 *
	 * @since 2.9.0
	 * @access public
	 * @var string
	 */
	var $commentmeta;

	/**
	 * WordPress Links table
	 *
	 * @since 1.5.0
	 * @access public
	 * @var string
	 */
	var $links;

	/**
	 * WordPress Options table
	 *
	 * @since 1.5.0
	 * @access public
	 * @var string
	 */
	var $options;

	/**
	 * WordPress Post Metadata table
	 *
	 * @since 1.5.0
	 * @access public
	 * @var string
	 */
	var $postmeta;

	/**
	 * WordPress Posts table
	 *
	 * @since 1.5.0
	 * @access public
	 * @var string
	 */
	var $posts;

	/**
	 * WordPress Terms table
	 *
	 * @since 2.3.0
	 * @access public
	 * @var string
	 */
	var $terms;

	/**
	 * WordPress Term Relationships table
	 *
	 * @since 2.3.0
	 * @access public
	 * @var string
	 */
	var $term_relationships;

	/**
	 * WordPress Term Taxonomy table
	 *
	 * @since 2.3.0
	 * @access public
	 * @var string
	 */
	var $term_taxonomy;

	/*
	 * Global and Multisite tables
	 */

	/**
	 * WordPress User Metadata table
	 *
	 * @since 2.3.0
	 * @access public
	 * @var string
	 */
	var $usermeta;

	/**
	 * WordPress Users table
	 *
	 * @since 1.5.0
	 * @access public
	 * @var string
	 */
	var $users;

	/**
	 * Multisite Blogs table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $blogs;

	/**
	 * Multisite Blog Versions table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $blog_versions;

	/**
	 * Multisite Registration Log table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $registration_log;

	/**
	 * Multisite Signups table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $signups;

	/**
	 * Multisite Sites table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $site;

	/**
	 * Multisite Sitewide Terms table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $sitecategories;

	/**
	 * Multisite Site Metadata table
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $sitemeta;

	/**
	 * Format specifiers for DB columns. Columns not listed here default to %s. Initialized during WP load.
	 *
	 * Keys are column names, values are format types: 'ID' => '%d'
	 *
	 * @since 2.8.0
	 * @see wpdb::prepare()
	 * @see wpdb::insert()
	 * @see wpdb::update()
	 * @see wpdb::delete()
	 * @see wp_set_wpdb_vars()
	 * @access public
	 * @var array
	 */
	var $field_types = array();

	/**
	 * Database table columns charset
	 *
	 * @since 2.2.0
	 * @access public
	 * @var string
	 */
	var $charset;

	/**
	 * Database table columns collate
	 *
	 * @since 2.2.0
	 * @access public
	 * @var string
	 */
	var $collate;

	/**
	 * Database Username
	 *
	 * @since 2.9.0
	 * @access protected
	 * @var string
	 */
	protected $dbuser;

	/**
	 * Database Password
	 *
	 * @since 3.1.0
	 * @access protected
	 * @var string
	 */
	protected $dbpassword;

	/**
	 * Database Name
	 *
	 * @since 3.1.0
	 * @access protected
	 * @var string
	 */
	protected $dbname;

	/**
	 * Database Host
	 *
	 * @since 3.1.0
	 * @access protected
	 * @var string
	 */
	protected $dbhost;

	/**
	 * Database Handle
	 *
	 * @since 0.71
	 * @access protected
	 * @var string
	 */
	protected $dbh;

	/**
	 * A textual description of the last query/get_row/get_var call
	 *
	 * @since 3.0.0
	 * @access public
	 * @var string
	 */
	var $func_call;

	/**
	 * Whether MySQL is used as the database engine.
	 *
	 * Set in WPDB::db_connect() to true, by default. This is used when checking
	 * against the required MySQL version for WordPress. Normally, a replacement
	 * database drop-in (db.php) will skip these checks, but setting this to true
	 * will force the checks to occur.
	 *
	 * @since 3.3.0
	 * @access public
	 * @var bool
	 */
	public $is_mysql = null;

	/**
	 * Connects to the database server and selects a database
	 *
	 * PHP5 style constructor for compatibility with PHP5. Does
	 * the actual setting up of the class properties and connection
	 * to the database.
	 *
	 * @link http://core.trac.wordpress.org/ticket/3354
	 * @since 2.0.8
	 *
	 * @param string $dbuser MySQL database user
	 * @param string $dbpassword MySQL database password
	 * @param string $dbname MySQL database name
	 * @param string $dbhost MySQL database host
	 */
	function __construct( $dbuser, $dbpassword, $dbname, $dbhost ) {
		register_shutdown_function( array( $this, '__destruct' ) );

		if ( WP_DEBUG && WP_DEBUG_DISPLAY )
			$this->show_errors();

		$this->init_charset();

		$this->dbuser = $dbuser;
		$this->dbpassword = $dbpassword;
		$this->dbname = $dbname;
		$this->dbhost = $dbhost;

		$this->db_connect();
	}

	/**
	 * PHP5 style destructor and will run when database object is destroyed.
	 *
	 * @see wpdb::__construct()
	 * @since 2.0.8
	 * @return bool true
	 */
	function __destruct() {
		return true;
	}

	/**
	 * PHP5 style magic getter, used to lazy-load expensive data.
	 *
	 * @since 3.5.0
	 *
	 * @param string $name The private member to get, and optionally process
	 * @return mixed The private member
	 */
	function __get( $name ) {
		if ( 'col_info' == $name )
			$this->load_col_info();

		return $this->$name;
	}

	/**
	 * Magic function, for backwards compatibility
	 *
	 * @since 3.5.0
	 *
	 * @param string $name  The private member to set
	 * @param mixed  $value The value to set
	 */
	function __set( $name, $value ) {
		$protected_members = array(
			'col_meta',
			'table_charset',
			'check_current_query',
		);
		if (  in_array( $name, $protected_members, true ) ) {
			return;
		}
		$this->$name = $value;
	}

	/**
	 * Magic function, for backwards compatibility
	 *
	 * @since 3.5.0
	 *
	 * @param string $name  The private member to check
	 *
	 * @return bool If the member is set or not
	 */
	function __isset( $name ) {
		return isset( $this->$name );
	}

	/**
	 * Magic function, for backwards compatibility
	 *
	 * @since 3.5.0
	 *
	 * @param string $name  The private member to unset
	 */
	function __unset( $name ) {
		unset( $this->$name );
	}

	/**
	 * Set $this->charset and $this->collate
	 *
	 * @since 3.1.0
	 */
	function init_charset() {
		if ( function_exists('is_multisite') && is_multisite() ) {
			$this->charset = 'utf8';
			if ( defined( 'DB_COLLATE' ) && DB_COLLATE )
				$this->collate = DB_COLLATE;
			else
				$this->collate = 'utf8_general_ci';
		} elseif ( defined( 'DB_COLLATE' ) ) {
			$this->collate = DB_COLLATE;
		}

		if ( defined( 'DB_CHARSET' ) )
			$this->charset = DB_CHARSET;
	}

	/**
	 * Sets the connection's character set.
	 *
	 * @since 3.1.0
	 *
	 * @param resource $dbh     The resource given by mysql_connect
	 * @param string   $charset The character set (optional)
	 * @param string   $collate The collation (optional)
	 */
	function set_charset( $dbh, $charset = null, $collate = null ) {
		if ( ! isset( $charset ) )
			$charset = $this->charset;
		if ( ! isset( $collate ) )
			$collate = $this->collate;
		if ( $this->has_cap( 'collation' ) && ! empty( $charset ) ) {
			if ( function_exists( 'mysql_set_charset' ) && $this->has_cap( 'set_charset' ) ) {
				mysql_set_charset( $charset, $dbh );
			} else {
				$query = $this->prepare( 'SET NAMES %s', $charset );
				if ( ! empty( $collate ) )
					$query .= $this->prepare( ' COLLATE %s', $collate );
				mysql_query( $query, $dbh );
			}
		}
	}

	/**
	 * Sets the table prefix for the WordPress tables.
	 *
	 * @since 2.5.0
	 *
	 * @param string $prefix Alphanumeric name for the new prefix.
	 * @param bool $set_table_names Optional. Whether the table names, e.g. wpdb::$posts, should be updated or not.
	 * @return string|WP_Error Old prefix or WP_Error on error
	 */
	function set_prefix( $prefix, $set_table_names = true ) {

		if ( preg_match( '|[^a-z0-9_]|i', $prefix ) )
			return new WP_Error('invalid_db_prefix', 'Invalid database prefix' );

		$old_prefix = is_multisite() ? '' : $prefix;

		if ( isset( $this->base_prefix ) )
			$old_prefix = $this->base_prefix;

		$this->base_prefix = $prefix;

		if ( $set_table_names ) {
			foreach ( $this->tables( 'global' ) as $table => $prefixed_table )
				$this->$table = $prefixed_table;

			if ( is_multisite() && empty( $this->blogid ) )
				return $old_prefix;

			$this->prefix = $this->get_blog_prefix();

			foreach ( $this->tables( 'blog' ) as $table => $prefixed_table )
				$this->$table = $prefixed_table;

			foreach ( $this->tables( 'old' ) as $table => $prefixed_table )
				$this->$table = $prefixed_table;
		}
		return $old_prefix;
	}

	/**
	 * Sets blog id.
	 *
	 * @since 3.0.0
	 * @access public
	 * @param int $blog_id
	 * @param int $site_id Optional.
	 * @return string previous blog id
	 */
	function set_blog_id( $blog_id, $site_id = 0 ) {
		if ( ! empty( $site_id ) )
			$this->siteid = $site_id;

		$old_blog_id  = $this->blogid;
		$this->blogid = $blog_id;

		$this->prefix = $this->get_blog_prefix();

		foreach ( $this->tables( 'blog' ) as $table => $prefixed_table )
			$this->$table = $prefixed_table;

		foreach ( $this->tables( 'old' ) as $table => $prefixed_table )
			$this->$table = $prefixed_table;

		return $old_blog_id;
	}

	/**
	 * Gets blog prefix.
	 *
	 * @uses is_multisite()
	 * @since 3.0.0
	 * @param int $blog_id Optional.
	 * @return string Blog prefix.
	 */
	function get_blog_prefix( $blog_id = null ) {
		if ( is_multisite() ) {
			if ( null === $blog_id )
				$blog_id = $this->blogid;
			$blog_id = (int) $blog_id;
			if ( defined( 'MULTISITE' ) && ( 0 == $blog_id || 1 == $blog_id ) )
				return $this->base_prefix;
			else
				return $this->base_prefix . $blog_id . '_';
		} else {
			return $this->base_prefix;
		}
	}

	/**
	 * Returns an array of WordPress tables.
	 *
	 * Also allows for the CUSTOM_USER_TABLE and CUSTOM_USER_META_TABLE to
	 * override the WordPress users and usermeta tables that would otherwise
	 * be determined by the prefix.
	 *
	 * The scope argument can take one of the following:
	 *
	 * 'all' - returns 'all' and 'global' tables. No old tables are returned.
	 * 'blog' - returns the blog-level tables for the queried blog.
	 * 'global' - returns the global tables for the installation, returning multisite tables only if running multisite.
	 * 'ms_global' - returns the multisite global tables, regardless if current installation is multisite.
	 * 'old' - returns tables which are deprecated.
	 *
	 * @since 3.0.0
	 * @uses wpdb::$tables
	 * @uses wpdb::$old_tables
	 * @uses wpdb::$global_tables
	 * @uses wpdb::$ms_global_tables
	 * @uses is_multisite()
	 *
	 * @param string $scope Optional. Can be all, global, ms_global, blog, or old tables. Defaults to all.
	 * @param bool $prefix Optional. Whether to include table prefixes. Default true. If blog
	 * 	prefix is requested, then the custom users and usermeta tables will be mapped.
	 * @param int $blog_id Optional. The blog_id to prefix. Defaults to wpdb::$blogid. Used only when prefix is requested.
	 * @return array Table names. When a prefix is requested, the key is the unprefixed table name.
	 */
	function tables( $scope = 'all', $prefix = true, $blog_id = 0 ) {
		switch ( $scope ) {
			case 'all' :
				$tables = array_merge( $this->global_tables, $this->tables );
				if ( is_multisite() )
					$tables = array_merge( $tables, $this->ms_global_tables );
				break;
			case 'blog' :
				$tables = $this->tables;
				break;
			case 'global' :
				$tables = $this->global_tables;
				if ( is_multisite() )
					$tables = array_merge( $tables, $this->ms_global_tables );
				break;
			case 'ms_global' :
				$tables = $this->ms_global_tables;
				break;
			case 'old' :
				$tables = $this->old_tables;
				break;
			default :
				return array();
				break;
		}

		if ( $prefix ) {
			if ( ! $blog_id )
				$blog_id = $this->blogid;
			$blog_prefix = $this->get_blog_prefix( $blog_id );
			$base_prefix = $this->base_prefix;
			$global_tables = array_merge( $this->global_tables, $this->ms_global_tables );
			foreach ( $tables as $k => $table ) {
				if ( in_array( $table, $global_tables ) )
					$tables[ $table ] = $base_prefix . $table;
				else
					$tables[ $table ] = $blog_prefix . $table;
				unset( $tables[ $k ] );
			}

			if ( isset( $tables['users'] ) && defined( 'CUSTOM_USER_TABLE' ) )
				$tables['users'] = CUSTOM_USER_TABLE;

			if ( isset( $tables['usermeta'] ) && defined( 'CUSTOM_USER_META_TABLE' ) )
				$tables['usermeta'] = CUSTOM_USER_META_TABLE;
		}

		return $tables;
	}

	/**
	 * Selects a database using the current database connection.
	 *
	 * The database name will be changed based on the current database
	 * connection. On failure, the execution will bail and display an DB error.
	 *
	 * @since 0.71
	 *
	 * @param string $db MySQL database name
	 * @param resource $dbh Optional link identifier.
	 * @return null Always null.
	 */
	function select( $db, $dbh = null ) {
		if ( is_null($dbh) )
			$dbh = $this->dbh;

		if ( !@mysql_select_db( $db, $dbh ) ) {
			$this->ready = false;
			wp_load_translations_early();
			$this->bail( sprintf( __( '<h1>Can&#8217;t select database</h1>
<p>We were able to connect to the database server (which means your username and password is okay) but not able to select the <code>%1$s</code> database.</p>
<ul>
<li>Are you sure it exists?</li>
<li>Does the user <code>%2$s</code> have permission to use the <code>%1$s</code> database?</li>
<li>On some systems the name of your database is prefixed with your username, so it would be like <code>username_%1$s</code>. Could that be the problem?</li>
</ul>
<p>If you don\'t know how to set up a database you should <strong>contact your host</strong>. If all else fails you may find help at the <a href="http://wordpress.org/support/">WordPress Support Forums</a>.</p>' ), htmlspecialchars( $db, ENT_QUOTES ), htmlspecialchars( $this->dbuser, ENT_QUOTES ) ), 'db_select_fail' );
			return;
		}
	}

	/**
	 * Do not use, deprecated.
	 *
	 * Use esc_sql() or wpdb::prepare() instead.
	 *
	 * @since 2.8.0
	 * @deprecated 3.6.0
	 * @see wpdb::prepare
	 * @see esc_sql()
	 * @access private
	 *
	 * @param string $string
	 * @return string
	 */
	function _weak_escape( $string ) {
		if ( func_num_args() === 1 && function_exists( '_deprecated_function' ) )
			_deprecated_function( __METHOD__, '3.6', 'wpdb::prepare() or esc_sql()' );
		return addslashes( $string );
	}

	/**
	 * Real escape, using mysqli_real_escape_string() or mysql_real_escape_string()
	 *
	 * @see mysqli_real_escape_string()
	 * @see mysql_real_escape_string()
	 * @since 2.8.0
	 * @access private
	 *
	 * @param  string $string to escape
	 * @return string escaped
	 */
	function _real_escape( $string ) {
		if ( $this->dbh ) {
			$escaped = mysql_real_escape_string( $string, $this->dbh );
		} else {
			$class = get_class( $this );
			if ( function_exists( '__' ) ) {
				/* translators: %s: database access abstraction class, usually wpdb or a class extending wpdb */
				_doing_it_wrong( $class, sprintf( __( '%s must set a database connection for use with escaping.' ), $class ), '3.6.0' );
			} else {
				_doing_it_wrong( $class, sprintf( '%s must set a database connection for use with escaping.', $class ), '3.6.0' );
			}
			$escaped = addslashes( $string );
		}

		return $this->add_placeholder_escape( $escaped );
	}

	/**
	 * Escape data. Works on arrays.
	 *
	 * @uses wpdb::_real_escape()
	 * @since  2.8.0
	 * @access private
	 *
	 * @param  string|array $data
	 * @return string|array escaped
	 */
	function _escape( $data ) {
		if ( is_array( $data ) ) {
			foreach ( $data as $k => $v ) {
				if ( is_array($v) )
					$data[$k] = $this->_escape( $v );
				else
					$data[$k] = $this->_real_escape( $v );
			}
		} else {
			$data = $this->_real_escape( $data );
		}

		return $data;
	}

	/**
	 * Do not use, deprecated.
	 *
	 * Use esc_sql() or wpdb::prepare() instead.
	 *
	 * @since 0.71
	 * @deprecated 3.6.0
	 * @see wpdb::prepare()
	 * @see esc_sql()
	 *
	 * @param mixed $data
	 * @return mixed
	 */
	function escape( $data ) {
		if ( func_num_args() === 1 && function_exists( '_deprecated_function' ) )
			_deprecated_function( __METHOD__, '3.6', 'wpdb::prepare() or esc_sql()' );
		if ( is_array( $data ) ) {
			foreach ( $data as $k => $v ) {
				if ( is_array( $v ) )
					$data[$k] = $this->escape( $v, 'recursive' );
				else
					$data[$k] = $this->_weak_escape( $v, 'internal' );
			}
		} else {
			$data = $this->_weak_escape( $data, 'internal' );
		}

		return $data;
	}

	/**
	 * Escapes content by reference for insertion into the database, for security
	 *
	 * @uses wpdb::_real_escape()
	 * @since 2.3.0
	 * @param string $string to escape
	 * @return void
	 */
	function escape_by_ref( &$string ) {
		if ( ! is_float( $string ) )
			$string = $this->_real_escape( $string );
	}

	/**
	 * Prepares a SQL query for safe execution. Uses sprintf()-like syntax.
	 *
	 * The following placeholders can be used in the query string:
	 *   %d (integer)
	 *   %f (float)
	 *   %s (string)
	 *
	 * All placeholders MUST be left unquoted in the query string. A corresponding argument MUST be passed for each placeholder.
	 *
	 * For compatibility with old behavior, numbered or formatted string placeholders (eg, %1$s, %5s) will not have quotes
	 * added by this function, so should be passed with appropriate quotes around them for your usage.
	 *
	 * Literal percentage signs (%) in the query string must be written as %%. Percentage wildcards (for example,
	 * to use in LIKE syntax) must be passed via a substitution argument containing the complete LIKE string, these
	 * cannot be inserted directly in the query string. Also see {@see esc_like()}.
	 *
	 * Arguments may be passed as individual arguments to the method, or as a single array containing all arguments. A combination
	 * of the two is not supported.
	 *
	 * Examples:
	 *     $wpdb->prepare( "SELECT * FROM `table` WHERE `column` = %s AND `field` = %d OR `other_field` LIKE %s", array( 'foo', 1337, '%bar' ) );
	 *     $wpdb->prepare( "SELECT DATE_FORMAT(`field`, '%%c') FROM `table` WHERE `column` = %s", 'foo' );
	 *
	 * @link https://secure.php.net/sprintf Description of syntax.
	 * @since 2.3.0
	 *
	 * @param string      $query    Query statement with sprintf()-like placeholders
	 * @param array|mixed $args     The array of variables to substitute into the query's placeholders if being called with an array of arguments,
	 *                              or the first variable to substitute into the query's placeholders if being called with individual arguments.
	 * @param mixed       $args,... further variables to substitute into the query's placeholders if being called wih individual arguments.
	 * @return string|void Sanitized query string, if there is a query to prepare.
	 */
	public function prepare( $query, $args ) {
		if ( is_null( $query ) ) {
			return;
		}

		// This is not meant to be foolproof -- but it will catch obviously incorrect usage.
		if ( strpos( $query, '%' ) === false ) {
			wp_load_translations_early();
			_doing_it_wrong( 'wpdb::prepare', sprintf( __( 'The query argument of %s must have a placeholder.' ), 'wpdb::prepare()' ), '3.9.0' );
		}

		$args = func_get_args();
		array_shift( $args );

		// If args were passed as an array (as in vsprintf), move them up.
		$passed_as_array = false;
		if ( is_array( $args[0] ) && count( $args ) == 1 ) {
			$passed_as_array = true;
			$args = $args[0];
		}

		foreach ( $args as $arg ) {
			if ( ! is_scalar( $arg ) && ! is_null( $arg ) ) {
				wp_load_translations_early();
				_doing_it_wrong( 'wpdb::prepare', sprintf( __( 'Unsupported value type (%s).' ), gettype( $arg ) ), '4.8.2' );
			}
		}

		/*
		 * Specify the formatting allowed in a placeholder. The following are allowed:
		 *
		 * - Sign specifier. eg, $+d
		 * - Numbered placeholders. eg, %1$s
		 * - Padding specifier, including custom padding characters. eg, %05s, %'#5s
		 * - Alignment specifier. eg, %05-s
		 * - Precision specifier. eg, %.2f
		 */
		$allowed_format = '(?:[1-9][0-9]*[$])?[-+0-9]*(?: |0|\'.)?[-+0-9]*(?:\.[0-9]+)?';

		/*
		 * If a %s placeholder already has quotes around it, removing the existing quotes and re-inserting them
		 * ensures the quotes are consistent.
		 *
		 * For backwards compatibility, this is only applied to %s, and not to placeholders like %1$s, which are frequently
		 * used in the middle of longer strings, or as table name placeholders.
		 */
		$query = str_replace( "'%s'", '%s', $query ); // Strip any existing single quotes.
		$query = str_replace( '"%s"', '%s', $query ); // Strip any existing double quotes.
		$query = preg_replace( '/(?<!%)%s/', "'%s'", $query ); // Quote the strings, avoiding escaped strings like %%s.

		$query = preg_replace( "/(?<!%)(%($allowed_format)?f)/" , '%\\2F', $query ); // Force floats to be locale unaware.

		$query = preg_replace( "/%(?:%|$|(?!($allowed_format)?[sdF]))/", '%%\\1', $query ); // Escape any unescaped percents.

		// Count the number of valid placeholders in the query.
		$placeholders = preg_match_all( "/(^|[^%]|(%%)+)%($allowed_format)?[sdF]/", $query, $matches );

		if ( count( $args ) !== $placeholders ) {
			if ( 1 === $placeholders && $passed_as_array ) {
				// If the passed query only expected one argument, but the wrong number of arguments were sent as an array, bail.
				wp_load_translations_early();
				_doing_it_wrong( 'wpdb::prepare', __( 'The query only expected one placeholder, but an array of multiple placeholders was sent.' ), '4.9.0' );

				return;
			} else {
				/*
				 * If we don't have the right number of placeholders, but they were passed as individual arguments,
				 * or we were expecting multiple arguments in an array, throw a warning.
				 */
				wp_load_translations_early();
				_doing_it_wrong( 'wpdb::prepare',
					/* translators: 1: number of placeholders, 2: number of arguments passed */
					sprintf( __( 'The query does not contain the correct number of placeholders (%1$d) for the number of arguments passed (%2$d).' ),
						$placeholders,
						count( $args ) ),
					'4.8.3'
				);
			}
		}

		array_walk( $args, array( $this, 'escape_by_ref' ) );
		$query = @vsprintf( $query, $args );

		return $this->add_placeholder_escape( $query );
	}

	/**
	 * Print SQL/DB error.
	 *
	 * @since 0.71
	 * @global array $EZSQL_ERROR Stores error information of query and error string
	 *
	 * @param string $str The error to display
	 * @return bool False if the showing of errors is disabled.
	 */
	function print_error( $str = '' ) {
		global $EZSQL_ERROR;

		if ( !$str )
			$str = mysql_error( $this->dbh );
		$EZSQL_ERROR[] = array( 'query' => $this->last_query, 'error_str' => $str );

		if ( $this->suppress_errors )
			return false;

		wp_load_translations_early();

		if ( $caller = $this->get_caller() )
			$error_str = sprintf( __( 'WordPress database error %1$s for query %2$s made by %3$s' ), $str, $this->last_query, $caller );
		else
			$error_str = sprintf( __( 'WordPress database error %1$s for query %2$s' ), $str, $this->last_query );

		error_log( $error_str );

		// Are we showing errors?
		if ( ! $this->show_errors )
			return false;

		// If there is an error then take note of it
		if ( is_multisite() ) {
			$msg = "WordPress database error: [$str]\n{$this->last_query}\n";
			if ( defined( 'ERRORLOGFILE' ) )
				error_log( $msg, 3, ERRORLOGFILE );
			if ( defined( 'DIEONDBERROR' ) )
				wp_die( $msg );
		} else {
			$str   = htmlspecialchars( $str, ENT_QUOTES );
			$query = htmlspecialchars( $this->last_query, ENT_QUOTES );

			print "<div id='error'>
			<p class='wpdberror'><strong>WordPress database error:</strong> [$str]<br />
			<code>$query</code></p>
			</div>";
		}
	}

	/**
	 * Enables showing of database errors.
	 *
	 * This function should be used only to enable showing of errors.
	 * wpdb::hide_errors() should be used instead for hiding of errors. However,
	 * this function can be used to enable and disable showing of database
	 * errors.
	 *
	 * @since 0.71
	 * @see wpdb::hide_errors()
	 *
	 * @param bool $show Whether to show or hide errors
	 * @return bool Old value for showing errors.
	 */
	function show_errors( $show = true ) {
		$errors = $this->show_errors;
		$this->show_errors = $show;
		return $errors;
	}

	/**
	 * Disables showing of database errors.
	 *
	 * By default database errors are not shown.
	 *
	 * @since 0.71
	 * @see wpdb::show_errors()
	 *
	 * @return bool Whether showing of errors was active
	 */
	function hide_errors() {
		$show = $this->show_errors;
		$this->show_errors = false;
		return $show;
	}

	/**
	 * Whether to suppress database errors.
	 *
	 * By default database errors are suppressed, with a simple
	 * call to this function they can be enabled.
	 *
	 * @since 2.5.0
	 * @see wpdb::hide_errors()
	 * @param bool $suppress Optional. New value. Defaults to true.
	 * @return bool Old value
	 */
	function suppress_errors( $suppress = true ) {
		$errors = $this->suppress_errors;
		$this->suppress_errors = (bool) $suppress;
		return $errors;
	}

	/**
	 * Kill cached query results.
	 *
	 * @since 0.71
	 * @return void
	 */
	function flush() {
		$this->last_result = array();
		$this->col_info    = null;
		$this->last_query  = null;
		$this->rows_affected = $this->num_rows = 0;
		$this->last_error  = '';

		if ( is_resource( $this->result ) )
			mysql_free_result( $this->result );
	}

	/**
	 * Connect to and select database
	 *
	 * @since 3.0.0
	 */
	function db_connect() {

		$this->is_mysql = true;

		$new_link = defined( 'MYSQL_NEW_LINK' ) ? MYSQL_NEW_LINK : true;
		$client_flags = defined( 'MYSQL_CLIENT_FLAGS' ) ? MYSQL_CLIENT_FLAGS : 0;

		if ( WP_DEBUG ) {
			$this->dbh = mysql_connect( $this->dbhost, $this->dbuser, $this->dbpassword, $new_link, $client_flags );
		} else {
			$this->dbh = @mysql_connect( $this->dbhost, $this->dbuser, $this->dbpassword, $new_link, $client_flags );
		}

		if ( !$this->dbh ) {
			wp_load_translations_early();
			$this->bail( sprintf( __( "
<h1>Error establishing a database connection</h1>
<p>This either means that the username and password information in your <code>wp-config.php</code> file is incorrect or we can't contact the database server at <code>%s</code>. This could mean your host's database server is down.</p>
<ul>
	<li>Are you sure you have the correct username and password?</li>
	<li>Are you sure that you have typed the correct hostname?</li>
	<li>Are you sure that the database server is running?</li>
</ul>
<p>If you're unsure what these terms mean you should probably contact your host. If you still need help you can always visit the <a href='http://wordpress.org/support/'>WordPress Support Forums</a>.</p>
" ), htmlspecialchars( $this->dbhost, ENT_QUOTES ) ), 'db_connect_fail' );

			return;
		}

		$this->set_charset( $this->dbh );

		$this->ready = true;

		$this->select( $this->dbname, $this->dbh );
	}

	/**
	 * Perform a MySQL database query, using current database connection.
	 *
	 * More information can be found on the codex page.
	 *
	 * @since 0.71
	 *
	 * @param string $query Database query
	 * @return int|false Number of rows affected/selected or false on error
	 */
	function query( $query ) {
		if ( ! $this->ready ) {
			$this->check_current_query = true;
			return false;
		}

		/**
		 * Filter the database query.
		 *
		 * Some queries are made before the plugins have been loaded, and thus cannot be filtered with this method.
		 *
		 * @since 2.1.0
		 * @param string $query Database query.
		 */
		$query = apply_filters( 'query', $query );

		$return_val = 0;
		$this->flush();

		// Log how the function was called
		$this->func_call = "\$db->query(\"$query\")";

		// If we're writing to the database, make sure the query will write safely.
		if ( $this->check_current_query && ! $this->check_ascii( $query ) ) {
			$stripped_query = $this->strip_invalid_text_from_query( $query );
			// strip_invalid_text_from_query() can perform queries, so we need
			// to flush again, just to make sure everything is clear.
			$this->flush();
			if ( $stripped_query !== $query ) {
				$this->insert_id = 0;
				return false;
			}
		}

		$this->check_current_query = true;

		// Keep track of the last query for debug..
		$this->last_query = $query;

		if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES )
			$this->timer_start();

		$this->result = @mysql_query( $query, $this->dbh );
		$this->num_queries++;

		if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES )
			$this->queries[] = array( $query, $this->timer_stop(), $this->get_caller() );

		// If there is an error then take note of it..
		if ( $this->last_error = mysql_error( $this->dbh ) ) {
			// Clear insert_id on a subsequent failed insert.
			if ( $this->insert_id && preg_match( '/^\s*(insert|replace)\s/i', $query ) )
				$this->insert_id = 0;

			$this->print_error();
			return false;
		}

		if ( preg_match( '/^\s*(create|alter|truncate|drop)\s/i', $query ) ) {
			$return_val = $this->result;
		} elseif ( preg_match( '/^\s*(insert|delete|update|replace)\s/i', $query ) ) {
			$this->rows_affected = mysql_affected_rows( $this->dbh );
			// Take note of the insert_id
			if ( preg_match( '/^\s*(insert|replace)\s/i', $query ) ) {
				$this->insert_id = mysql_insert_id($this->dbh);
			}
			// Return number of rows affected
			$return_val = $this->rows_affected;
		} else {
			$num_rows = 0;
			while ( $row = @mysql_fetch_object( $this->result ) ) {
				$this->last_result[$num_rows] = $row;
				$num_rows++;
			}

			// Log number of rows the query returned
			// and return number of rows selected
			$this->num_rows = $num_rows;
			$return_val     = $num_rows;
		}

		return $return_val;
	}

	/**
	 * Generates and returns a placeholder escape string for use in queries returned by ::prepare().
	 *
	 * @since 4.8.3
	 *
	 * @return string String to escape placeholders.
	 */
	public function placeholder_escape() {
		static $placeholder;

		if ( ! $placeholder ) {
			// If ext/hash is not present, compat.php's hash_hmac() does not support sha256.
			$algo = function_exists( 'hash' ) ? 'sha256' : 'sha1';
			// Old WP installs may not have AUTH_SALT defined.
			$salt = defined( 'AUTH_SALT' ) && AUTH_SALT ? AUTH_SALT : (string) rand();

			$placeholder = '{' . hash_hmac( $algo, uniqid( $salt, true ), $salt ) . '}';
		}

		/*
		 * Add the filter to remove the placeholder escaper. Uses priority 0, so that anything
		 * else attached to this filter will recieve the query with the placeholder string removed.
		 */
		if ( ! has_filter( 'query', array( $this, 'remove_placeholder_escape' ) ) ) {
			add_filter( 'query', array( $this, 'remove_placeholder_escape' ), 0 );
		}

		return $placeholder;
	}

	/**
	 * Adds a placeholder escape string, to escape anything that resembles a printf() placeholder.
	 *
	 * @since 4.8.3
	 *
	 * @param string $query The query to escape.
	 * @return string The query with the placeholder escape string inserted where necessary.
	 */
	public function add_placeholder_escape( $query ) {
		/*
		 * To prevent returning anything that even vaguely resembles a placeholder,
		 * we clobber every % we can find.
		 */
		return str_replace( '%', $this->placeholder_escape(), $query );
	}

	/**
	 * Removes the placeholder escape strings from a query.
	 *
	 * @since 4.8.3
	 *
	 * @param string $query The query from which the placeholder will be removed.
	 * @return string The query with the placeholder removed.
	 */
	public function remove_placeholder_escape( $query ) {
		return str_replace( $this->placeholder_escape(), '%', $query );
	}

	/**
	 * Insert a row into a table.
	 *
	 * <code>
	 * wpdb::insert( 'table', array( 'column' => 'foo', 'field' => 'bar' ) )
	 * wpdb::insert( 'table', array( 'column' => 'foo', 'field' => 1337 ), array( '%s', '%d' ) )
	 * </code>
	 *
	 * @since 2.5.0
	 * @see wpdb::prepare()
	 * @see wpdb::$field_types
	 * @see wp_set_wpdb_vars()
	 *
	 * @param string $table table name
	 * @param array $data Data to insert (in column => value pairs). Both $data columns and $data values should be "raw" (neither should be SQL escaped).
	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data. If string, that format will be used for all of the values in $data.
	 * 	A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
	 * @return int|false The number of rows inserted, or false on error.
	 */
	function insert( $table, $data, $format = null ) {
		return $this->_insert_replace_helper( $table, $data, $format, 'INSERT' );
	}

	/**
	 * Replace a row into a table.
	 *
	 * <code>
	 * wpdb::replace( 'table', array( 'column' => 'foo', 'field' => 'bar' ) )
	 * wpdb::replace( 'table', array( 'column' => 'foo', 'field' => 1337 ), array( '%s', '%d' ) )
	 * </code>
	 *
	 * @since 3.0.0
	 * @see wpdb::prepare()
	 * @see wpdb::$field_types
	 * @see wp_set_wpdb_vars()
	 *
	 * @param string $table table name
	 * @param array $data Data to insert (in column => value pairs). Both $data columns and $data values should be "raw" (neither should be SQL escaped).
	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data. If string, that format will be used for all of the values in $data.
	 * 	A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
	 * @return int|false The number of rows affected, or false on error.
	 */
	function replace( $table, $data, $format = null ) {
		return $this->_insert_replace_helper( $table, $data, $format, 'REPLACE' );
	}

	/**
	 * Helper function for insert and replace.
	 *
	 * Runs an insert or replace query based on $type argument.
	 *
	 * @access private
	 * @since 3.0.0
	 * @see wpdb::prepare()
	 * @see wpdb::$field_types
	 * @see wp_set_wpdb_vars()
	 *
	 * @param string $table table name
	 * @param array $data Data to insert (in column => value pairs). Both $data columns and $data values should be "raw" (neither should be SQL escaped).
	 * @param array|string $format Optional. An array of formats to be mapped to each of the value in $data. If string, that format will be used for all of the values in $data.
	 * 	A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
	 * @param string $type Optional. What type of operation is this? INSERT or REPLACE. Defaults to INSERT.
	 * @return int|false The number of rows affected, or false on error.
	 */
	function _insert_replace_helper( $table, $data, $format = null, $type = 'INSERT' ) {
		$this->insert_id = 0;

		if ( ! in_array( strtoupper( $type ), array( 'REPLACE', 'INSERT' ) ) ) {
			return false;
		}

		$data = $this->process_fields( $table, $data, $format );
		if ( false === $data ) {
			return false;
		}

		$formats = $values = array();
		foreach ( $data as $value ) {
			$formats[] = $value['format'];
			$values[]  = $value['value'];
		}

		$fields  = '`' . implode( '`, `', array_keys( $data ) ) . '`';
		$formats = implode( ', ', $formats );

		$sql = "$type INTO `$table` ($fields) VALUES ($formats)";

		$this->check_current_query = false;
		return $this->query( $this->prepare( $sql, $values ) );
	}

	/**
	 * Update a row in the table
	 *
	 * <code>
	 * wpdb::update( 'table', array( 'column' => 'foo', 'field' => 'bar' ), array( 'ID' => 1 ) )
	 * wpdb::update( 'table', array( 'column' => 'foo', 'field' => 1337 ), array( 'ID' => 1 ), array( '%s', '%d' ), array( '%d' ) )
	 * </code>
	 *
	 * @since 2.5.0
	 * @see wpdb::prepare()
	 * @see wpdb::$field_types
	 * @see wp_set_wpdb_vars()
	 *
	 * @param string $table table name
	 * @param array $data Data to update (in column => value pairs). Both $data columns and $data values should be "raw" (neither should be SQL escaped).
	 * @param array $where A named array of WHERE clauses (in column => value pairs). Multiple clauses will be joined with ANDs. Both $where columns and $where values should be "raw".
	 * @param array|string $format Optional. An array of formats to be mapped to each of the values in $data. If string, that format will be used for all of the values in $data.
	 * 	A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $data will be treated as strings unless otherwise specified in wpdb::$field_types.
	 * @param array|string $where_format Optional. An array of formats to be mapped to each of the values in $where. If string, that format will be used for all of the items in $where. A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $where will be treated as strings.
	 * @return int|false The number of rows updated, or false on error.
	 */
	function update( $table, $data, $where, $format = null, $where_format = null ) {
		if ( ! is_array( $data ) || ! is_array( $where ) ) {
			return false;
		}

		$data = $this->process_fields( $table, $data, $format );
		if ( false === $data ) {
			return false;
		}
		$where = $this->process_fields( $table, $where, $where_format );
		if ( false === $where ) {
			return false;
		}

		$fields = $conditions = $values = array();
		foreach ( $data as $field => $value ) {
			$fields[] = "`$field` = " . $value['format'];
			$values[] = $value['value'];
		}
		foreach ( $where as $field => $value ) {
			$conditions[] = "`$field` = " . $value['format'];
			$values[] = $value['value'];
		}

		$fields = implode( ', ', $fields );
		$conditions = implode( ' AND ', $conditions );

		$sql = "UPDATE `$table` SET $fields WHERE $conditions";

		$this->check_current_query = false;
		return $this->query( $this->prepare( $sql, $values ) );
	}

	/**
	 * Delete a row in the table
	 *
	 * <code>
	 * wpdb::delete( 'table', array( 'ID' => 1 ) )
	 * wpdb::delete( 'table', array( 'ID' => 1 ), array( '%d' ) )
	 * </code>
	 *
	 * @since 3.4.0
	 * @see wpdb::prepare()
	 * @see wpdb::$field_types
	 * @see wp_set_wpdb_vars()
	 *
	 * @param string $table table name
	 * @param array $where A named array of WHERE clauses (in column => value pairs). Multiple clauses will be joined with ANDs. Both $where columns and $where values should be "raw".
	 * @param array|string $where_format Optional. An array of formats to be mapped to each of the values in $where. If string, that format will be used for all of the items in $where. A format is one of '%d', '%f', '%s' (integer, float, string). If omitted, all values in $where will be treated as strings unless otherwise specified in wpdb::$field_types.
	 * @return int|false The number of rows updated, or false on error.
	 */
	function delete( $table, $where, $where_format = null ) {
		if ( ! is_array( $where ) ) {
			return false;
		}

		$where = $this->process_fields( $table, $where, $where_format );
		if ( false === $where ) {
			return false;
		}

		$conditions = $values = array();
		foreach ( $where as $field => $value ) {
			$conditions[] = "`$field` = " . $value['format'];
			$values[] = $value['value'];
		}

		$conditions = implode( ' AND ', $conditions );

		$sql = "DELETE FROM `$table` WHERE $conditions";

		$this->check_current_query = false;
		return $this->query( $this->prepare( $sql, $values ) );
	}


	/**
	 * Processes arrays of field/value pairs and field formats.
	 *
	 * This is a helper method for wpdb's CRUD methods, which take field/value
	 * pairs for inserts, updates, and where clauses. This method first pairs
	 * each value with a format. Then it determines the charset of that field,
	 * using that to determine if any invalid text would be stripped. If text is
	 * stripped, then field processing is rejected and the query fails.
	 *
	 * @since 4.2.0
	 * @access protected
	 *
	 * @param string $table  Table name.
	 * @param array  $data   Field/value pair.
	 * @param mixed  $format Format for each field.
	 * @return array|bool Returns an array of fields that contain paired values
	 *                    and formats. Returns false for invalid values.
	 */
	protected function process_fields( $table, $data, $format ) {
		$data = $this->process_field_formats( $data, $format );
		if ( false === $data ) {
			return false;
		}

		$data = $this->process_field_charsets( $data, $table );
		if ( false === $data ) {
			return false;
		}

		$data = $this->process_field_lengths( $data, $table );
		if ( false === $data ) {
			return false;
		}

		$converted_data = $this->strip_invalid_text( $data );

		if ( $data !== $converted_data ) {
			return false;
		}

		return $data;
	}

	/**
	 * Prepares arrays of value/format pairs as passed to wpdb CRUD methods.
	 *
	 * @since 4.2.0
	 * @access protected
	 *
	 * @param array $data   Array of fields to values.
	 * @param mixed $format Formats to be mapped to the values in $data.
	 * @return array Array, keyed by field names with values being an array
	 *               of 'value' and 'format' keys.
	 */
	protected function process_field_formats( $data, $format ) {
		$formats = $original_formats = (array) $format;

		foreach ( $data as $field => $value ) {
			$value = array(
				'value'  => $value,
				'format' => '%s',
			);

			if ( ! empty( $format ) ) {
				$value['format'] = array_shift( $formats );
				if ( ! $value['format'] ) {
					$value['format'] = reset( $original_formats );
				}
			} elseif ( isset( $this->field_types[ $field ] ) ) {
				$value['format'] = $this->field_types[ $field ];
			}

			$data[ $field ] = $value;
		}

		return $data;
	}

	/**
	 * Adds field charsets to field/value/format arrays generated by
	 * the {@see wpdb::process_field_formats()} method.
	 *
	 * @since 4.2.0
	 * @access protected
	 *
	 * @param array  $data  As it comes from the {@see wpdb::process_field_formats()} method.
	 * @param string $table Table name.
	 * @return The same array as $data with additional 'charset' keys.
	 */
	protected function process_field_charsets( $data, $table ) {
		foreach ( $data as $field => $value ) {
			if ( '%d' === $value['format'] || '%f' === $value['format'] ) {
				// We can skip this field if we know it isn't a string.
				// This checks %d/%f versus ! %s because it's sprintf() could take more.
				$value['charset'] = false;
			} else {
				$value['charset'] = $this->get_col_charset( $table, $field );
				if ( is_wp_error( $value['charset'] ) ) {
					return false;
				}
			}

			$data[ $field ] = $value;
		}

		return $data;
	}

	/**
	 * For string fields, record the maximum string length that field can safely save.
	 *
	 * @since 4.2.1
	 * @access protected
	 *
	 * @param array  $data  As it comes from the wpdb::process_field_charsets() method.
	 * @param string $table Table name.
	 * @return array|False The same array as $data with additional 'length' keys, or false if
	 *                     any of the values were too long for their corresponding field.
	 */
	protected function process_field_lengths( $data, $table ) {
		foreach ( $data as $field => $value ) {
			if ( '%d' === $value['format'] || '%f' === $value['format'] ) {
				// We can skip this field if we know it isn't a string.
				// This checks %d/%f versus ! %s because it's sprintf() could take more.
				$value['length'] = false;
			} else {
				$value['length'] = $this->get_col_length( $table, $field );
				if ( is_wp_error( $value['length'] ) ) {
					return false;
				}
			}

			$data[ $field ] = $value;
		}

		return $data;
	}

	/**
	 * Retrieve one variable from the database.
	 *
	 * Executes a SQL query and returns the value from the SQL result.
	 * If the SQL result contains more than one column and/or more than one row, this function returns the value in the column and row specified.
	 * If $query is null, this function returns the value in the specified column and row from the previous SQL result.
	 *
	 * @since 0.71
	 *
	 * @param string|null $query Optional. SQL query. Defaults to null, use the result from the previous query.
	 * @param int $x Optional. Column of value to return. Indexed from 0.
	 * @param int $y Optional. Row of value to return. Indexed from 0.
	 * @return string|null Database query result (as string), or null on failure
	 */
	function get_var( $query = null, $x = 0, $y = 0 ) {
		$this->func_call = "\$db->get_var(\"$query\", $x, $y)";

		if ( $this->check_safe_collation( $query ) ) {
			$this->check_current_query = false;
		}

		if ( $query )
			$this->query( $query );

		// Extract var out of cached results based x,y vals
		if ( !empty( $this->last_result[$y] ) ) {
			$values = array_values( get_object_vars( $this->last_result[$y] ) );
		}

		// If there is a value return it else return null
		return ( isset( $values[$x] ) && $values[$x] !== '' ) ? $values[$x] : null;
	}

	/**
	 * Retrieve one row from the database.
	 *
	 * Executes a SQL query and returns the row from the SQL result.
	 *
	 * @since 0.71
	 *
	 * @param string|null $query SQL query.
	 * @param string $output Optional. one of ARRAY_A | ARRAY_N | OBJECT constants. Return an associative array (column => value, ...),
	 * 	a numerically indexed array (0 => value, ...) or an object ( ->column = value ), respectively.
	 * @param int $y Optional. Row to return. Indexed from 0.
	 * @return mixed Database query result in format specified by $output or null on failure
	 */
	function get_row( $query = null, $output = OBJECT, $y = 0 ) {
		$this->func_call = "\$db->get_row(\"$query\",$output,$y)";

		if ( $this->check_safe_collation( $query ) ) {
			$this->check_current_query = false;
		}

		if ( $query )
			$this->query( $query );
		else
			return null;

		if ( !isset( $this->last_result[$y] ) )
			return null;

		if ( $output == OBJECT ) {
			return $this->last_result[$y] ? $this->last_result[$y] : null;
		} elseif ( $output == ARRAY_A ) {
			return $this->last_result[$y] ? get_object_vars( $this->last_result[$y] ) : null;
		} elseif ( $output == ARRAY_N ) {
			return $this->last_result[$y] ? array_values( get_object_vars( $this->last_result[$y] ) ) : null;
		} else {
			$this->print_error( " \$db->get_row(string query, output type, int offset) -- Output type must be one of: OBJECT, ARRAY_A, ARRAY_N" );
		}
	}

	/**
	 * Retrieve one column from the database.
	 *
	 * Executes a SQL query and returns the column from the SQL result.
	 * If the SQL result contains more than one column, this function returns the column specified.
	 * If $query is null, this function returns the specified column from the previous SQL result.
	 *
	 * @since 0.71
	 *
	 * @param string|null $query Optional. SQL query. Defaults to previous query.
	 * @param int $x Optional. Column to return. Indexed from 0.
	 * @return array Database query result. Array indexed from 0 by SQL result row number.
	 */
	function get_col( $query = null , $x = 0 ) {
		if ( $this->check_safe_collation( $query ) ) {
			$this->check_current_query = false;
		}

		if ( $query )
			$this->query( $query );

		$new_array = array();
		// Extract the column values
		for ( $i = 0, $j = count( $this->last_result ); $i < $j; $i++ ) {
			$new_array[$i] = $this->get_var( null, $x, $i );
		}
		return $new_array;
	}

	/**
	 * Retrieve an entire SQL result set from the database (i.e., many rows)
	 *
	 * Executes a SQL query and returns the entire SQL result.
	 *
	 * @since 0.71
	 *
	 * @param string $query SQL query.
	 * @param string $output Optional. Any of ARRAY_A | ARRAY_N | OBJECT | OBJECT_K constants. With one of the first three, return an array of rows indexed from 0 by SQL result row number.
	 * 	Each row is an associative array (column => value, ...), a numerically indexed array (0 => value, ...), or an object. ( ->column = value ), respectively.
	 * 	With OBJECT_K, return an associative array of row objects keyed by the value of each row's first column's value. Duplicate keys are discarded.
	 * @return mixed Database query results
	 */
	function get_results( $query = null, $output = OBJECT ) {
		$this->func_call = "\$db->get_results(\"$query\", $output)";

		if ( $this->check_safe_collation( $query ) ) {
			$this->check_current_query = false;
		}

		if ( $query )
			$this->query( $query );
		else
			return null;

		$new_array = array();
		if ( $output == OBJECT ) {
			// Return an integer-keyed array of row objects
			return $this->last_result;
		} elseif ( $output == OBJECT_K ) {
			// Return an array of row objects with keys from column 1
			// (Duplicates are discarded)
			foreach ( $this->last_result as $row ) {
				$var_by_ref = get_object_vars( $row );
				$key = array_shift( $var_by_ref );
				if ( ! isset( $new_array[ $key ] ) )
					$new_array[ $key ] = $row;
			}
			return $new_array;
		} elseif ( $output == ARRAY_A || $output == ARRAY_N ) {
			// Return an integer-keyed array of...
			if ( $this->last_result ) {
				foreach( (array) $this->last_result as $row ) {
					if ( $output == ARRAY_N ) {
						// ...integer-keyed row arrays
						$new_array[] = array_values( get_object_vars( $row ) );
					} else {
						// ...column name-keyed row arrays
						$new_array[] = get_object_vars( $row );
					}
				}
			}
			return $new_array;
		}
		return null;
	}


	/**
	 * Retrieves the character set for the given table.
	 *
	 * @since 4.2.0
	 * @access protected
	 *
	 * @param string $table Table name.
	 * @return string|WP_Error Table character set, {@see WP_Error} object if it couldn't be found.
	 */
	protected function get_table_charset( $table ) {
		$tablekey = strtolower( $table );

		/**
		 * Filter the table charset value before the DB is checked.
		 *
		 * Passing a non-null value to the filter will effectively short-circuit
		 * checking the DB for the charset, returning that value instead.
		 *
		 * @since 4.2.0
		 *
		 * @param string $charset The character set to use. Default null.
		 * @param string $table   The name of the table being checked.
		 */
		$charset = apply_filters( 'pre_get_table_charset', null, $table );
		if ( null !== $charset ) {
			return $charset;
		}

		if ( isset( $this->table_charset[ $tablekey ] ) ) {
			return $this->table_charset[ $tablekey ];
		}

		$charsets = $columns = array();

		$table_parts = explode( '.', $table );
		$table = '`' . implode( '`.`', $table_parts ) . '`';
		$results = $this->get_results( "SHOW FULL COLUMNS FROM $table" );
		if ( ! $results ) {
			return new WP_Error( 'wpdb_get_table_charset_failure' );
		}

		foreach ( $results as $column ) {
			$columns[ strtolower( $column->Field ) ] = $column;
		}

		$this->col_meta[ $tablekey ] = $columns;

		foreach ( $columns as $column ) {
			if ( ! empty( $column->Collation ) ) {
				list( $charset ) = explode( '_', $column->Collation );
				$charsets[ strtolower( $charset ) ] = true;
			}

			list( $type ) = explode( '(', $column->Type );

			// A binary/blob means the whole query gets treated like this.
			if ( in_array( strtoupper( $type ), array( 'BINARY', 'VARBINARY', 'TINYBLOB', 'MEDIUMBLOB', 'BLOB', 'LONGBLOB' ) ) ) {
				$this->table_charset[ $tablekey ] = 'binary';
				return 'binary';
			}
		}

		// utf8mb3 is an alias for utf8.
		if ( isset( $charsets['utf8mb3'] ) ) {
			$charsets['utf8'] = true;
			unset( $charsets['utf8mb3'] );
		}

		// Check if we have more than one charset in play.
		$count = count( $charsets );
		if ( 1 === $count ) {
			$charset = key( $charsets );
		} elseif ( 0 === $count ) {
			// No charsets, assume this table can store whatever.
			$charset = false;
		} else {
			// More than one charset. Remove latin1 if present and recalculate.
			unset( $charsets['latin1'] );
			$count = count( $charsets );
			if ( 1 === $count ) {
				// Only one charset (besides latin1).
				$charset = key( $charsets );
			} elseif ( 2 === $count && isset( $charsets['utf8'], $charsets['utf8mb4'] ) ) {
				// Two charsets, but they're utf8 and utf8mb4, use utf8.
				$charset = 'utf8';
			} else {
				// Two mixed character sets. ascii.
				$charset = 'ascii';
			}
		}

		$this->table_charset[ $tablekey ] = $charset;
		return $charset;
	}

	/**
	 * Retrieves the character set for the given column.
	 *
	 * @since 4.2.0
	 * @access public
	 *
	 * @param string $table  Table name.
	 * @param string $column Column name.
	 * @return mixed Column character set as a string. False if the column has no
	 *               character set. {@see WP_Error} object if there was an error.
	 */
	public function get_col_charset( $table, $column ) {
		$tablekey = strtolower( $table );
		$columnkey = strtolower( $column );

		/**
		 * Filter the column charset value before the DB is checked.
		 *
		 * Passing a non-null value to the filter will short-circuit
		 * checking the DB for the charset, returning that value instead.
		 *
		 * @since 4.2.0
		 *
		 * @param string $charset The character set to use. Default null.
		 * @param string $table   The name of the table being checked.
		 * @param string $column  The name of the column being checked.
		 */
		$charset = apply_filters( 'pre_get_col_charset', null, $table, $column );
		if ( null !== $charset ) {
			return $charset;
		}

		// Skip this entirely if this isn't a MySQL database.
		if ( false === $this->is_mysql ) {
			return false;
		}

		if ( empty( $this->table_charset[ $tablekey ] ) ) {
			// This primes column information for us.
			$table_charset = $this->get_table_charset( $table );
			if ( is_wp_error( $table_charset ) ) {
				return $table_charset;
			}
		}

		// If still no column information, return the table charset.
		if ( empty( $this->col_meta[ $tablekey ] ) ) {
			return $this->table_charset[ $tablekey ];
		}

		// If this column doesn't exist, return the table charset.
		if ( empty( $this->col_meta[ $tablekey ][ $columnkey ] ) ) {
			return $this->table_charset[ $tablekey ];
		}

		// Return false when it's not a string column.
		if ( empty( $this->col_meta[ $tablekey ][ $columnkey ]->Collation ) ) {
			return false;
		}

		list( $charset ) = explode( '_', $this->col_meta[ $tablekey ][ $columnkey ]->Collation );
		return $charset;
	}

	/**
	 * Retrieve the maximum string length allowed in a given column.
	 * The length may either be specified as a byte length or a character length.
	 *
	 * @since 4.2.1
	 * @access public
	 *
	 * @param string $table  Table name.
	 * @param string $column Column name.
	 * @return mixed array( 'length' => (int), 'type' => 'byte' | 'char' )
	 *               false if the column has no length (for example, numeric column)
	 *               WP_Error object if there was an error.
	 */
	public function get_col_length( $table, $column ) {
		$tablekey = strtolower( $table );
		$columnkey = strtolower( $column );

		// Skip this entirely if this isn't a MySQL database.
		if ( false === $this->is_mysql ) {
			return false;
		}

		if ( empty( $this->col_meta[ $tablekey ] ) ) {
			// This primes column information for us.
			$table_charset = $this->get_table_charset( $table );
			if ( is_wp_error( $table_charset ) ) {
				return $table_charset;
			}
		}

		if ( empty( $this->col_meta[ $tablekey ][ $columnkey ] ) ) {
			return false;
		}

		$typeinfo = explode( '(', $this->col_meta[ $tablekey ][ $columnkey ]->Type );

		$type = strtolower( $typeinfo[0] );
		if ( ! empty( $typeinfo[1] ) ) {
			$length = trim( $typeinfo[1], ')' );
		} else {
			$length = false;
		}

		switch( $type ) {
			case 'char':
			case 'varchar':
				return array(
					'type'   => 'char',
					'length' => (int) $length,
				);
				break;
			case 'binary':
			case 'varbinary':
				return array(
					'type'   => 'byte',
					'length' => (int) $length,
				);
				break;
			case 'tinyblob':
			case 'tinytext':
				return array(
					'type'   => 'byte',
					'length' => 255,        // 2^8 - 1
				);
				break;
			case 'blob':
			case 'text':
				return array(
					'type'   => 'byte',
					'length' => 65535,      // 2^16 - 1
				);
				break;
			case 'mediumblob':
			case 'mediumtext':
				return array(
					'type'   => 'byte',
					'length' => 16777215,   // 2^24 - 1
				);
				break;
			case 'longblob':
			case 'longtext':
				return array(
					'type'   => 'byte',
					'length' => 4294967295, // 2^32 - 1
				);
				break;
			default:
				return false;
		}

		return false;
	}

	/**
	 * Check if a string is ASCII.
	 *
	 * The negative regex is faster for non-ASCII strings, as it allows
	 * the search to finish as soon as it encounters a non-ASCII character.
	 *
	 * @since 4.2.0
	 * @access protected
	 *
	 * @param string $string String to check.
	 * @return bool True if ASCII, false if not.
	 */
	protected function check_ascii( $string ) {
		if ( function_exists( 'mb_check_encoding' ) ) {
			if ( mb_check_encoding( $string, 'ASCII' ) ) {
				return true;
			}
		} elseif ( ! preg_match( '/[^\x00-\x7F]/', $string ) ) {
			return true;
		}

		return false;
	}

	/**
	 * Check if the query is accessing a collation considered safe on the current version of MySQL.
	 *
	 * @since 4.2.0
	 * @access protected
	 *
	 * @param string $query The query to check.
	 * @return bool True if the collation is safe, false if it isn't.
	 */
	protected function check_safe_collation( $query ) {
		if ( $this->checking_collation ) {
			return true;
		}

		// We don't need to check the collation for queries that don't read data.
		$query = ltrim( $query, "\r\n\t (" );
		if ( preg_match( '/^(?:SHOW|DESCRIBE|DESC|EXPLAIN|CREATE)\s/i', $query ) ) {
			return true;
		}

		// All-ASCII queries don't need extra checking.
		if ( $this->check_ascii( $query ) ) {
			return true;
		}

		$table = $this->get_table_from_query( $query );
		if ( ! $table ) {
			return false;
		}

		$this->checking_collation = true;
		$collation = $this->get_table_charset( $table );
		$this->checking_collation = false;

		// Tables with no collation, or latin1 only, don't need extra checking.
		if ( false === $collation || 'latin1' === $collation ) {
			return true;
		}

		$table = strtolower( $table );
		if ( empty( $this->col_meta[ $table ] ) ) {
			return false;
		}

		// If any of the columns don't have one of these collations, it needs more sanity checking.
		foreach( $this->col_meta[ $table ] as $col ) {
			if ( empty( $col->Collation ) ) {
				continue;
			}

			if ( ! in_array( $col->Collation, array( 'utf8_general_ci', 'utf8_bin', 'utf8mb4_general_ci', 'utf8mb4_bin' ), true ) ) {
				return false;
			}
		}

		return true;
	}

	/**
	 * Strips any invalid characters based on value/charset pairs.
	 *
	 * @since 4.2.0
	 * @access protected
	 *
	 * @param array $data Array of value arrays. Each value array has the keys
	 *                    'value' and 'charset'. An optional 'ascii' key can be
	 *                    set to false to avoid redundant ASCII checks.
	 * @return array|WP_Error The $data parameter, with invalid characters removed from
	 *                        each value. This works as a passthrough: any additional keys
	 *                        such as 'field' are retained in each value array. If we cannot
	 *                        remove invalid characters, a {@see WP_Error} object is returned.
	 */
		// If any of the columns don't have one of these collations, it needs more sanity checking.
	protected function strip_invalid_text( $data ) {
		$db_check_string = false;

		foreach ( $data as &$value ) {
			$charset = $value['charset'];

			if ( is_array( $value['length'] ) ) {
				$length = $value['length']['length'];
			} else {
				$length = false;
			}

			// There's no charset to work with.
			if ( false === $charset ) {
				continue;
			}

			// Column isn't a string.
			if ( ! is_string( $value['value'] ) ) {
				continue;
			}

			$truncate_by_byte_length = 'byte' === $value['length']['type'];

			$needs_validation = true;
			if (
				// latin1 can store any byte sequence
				'latin1' === $charset
			||
				// ASCII is always OK.
				( ! isset( $value['ascii'] ) && $this->check_ascii( $value['value'] ) )
			) {
				$truncate_by_byte_length = true;
				$needs_validation = false;
			}

			if ( $truncate_by_byte_length ) {
				mbstring_binary_safe_encoding();
				if ( false !== $length && strlen( $value['value'] ) > $length ) {
					$value['value'] = substr( $value['value'], 0, $length );
				}
				reset_mbstring_encoding();

				if ( ! $needs_validation ) {
					continue;
				}
			}

			// utf8 can be handled by regex, which is a bunch faster than a DB lookup.
			if ( ( 'utf8' === $charset || 'utf8mb3' === $charset || 'utf8mb4' === $charset ) && function_exists( 'mb_strlen' ) ) {
				$regex = '/
					(
						(?: [\x00-\x7F]                  # single-byte sequences   0xxxxxxx
						|   [\xC2-\xDF][\x80-\xBF]       # double-byte sequences   110xxxxx 10xxxxxx
						|   \xE0[\xA0-\xBF][\x80-\xBF]   # triple-byte sequences   1110xxxx 10xxxxxx * 2
						|   [\xE1-\xEC][\x80-\xBF]{2}
						|   \xED[\x80-\x9F][\x80-\xBF]
						|   [\xEE-\xEF][\x80-\xBF]{2}';

				if ( 'utf8mb4' === $charset ) {
					$regex .= '
						|    \xF0[\x90-\xBF][\x80-\xBF]{2} # four-byte sequences   11110xxx 10xxxxxx * 3
						|    [\xF1-\xF3][\x80-\xBF]{3}
						|    \xF4[\x80-\x8F][\x80-\xBF]{2}
					';
				}

				$regex .= '){1,40}                          # ...one or more times
					)
					| .                                  # anything else
					/x';
				$value['value'] = preg_replace( $regex, '$1', $value['value'] );


				if ( false !== $length && mb_strlen( $value['value'], 'UTF-8' ) > $length ) {
					$value['value'] = mb_substr( $value['value'], 0, $length, 'UTF-8' );
				}
				continue;
			}

			// We couldn't use any local conversions, send it to the DB.
			$value['db'] = $db_check_string = true;
		}
		unset( $value ); // Remove by reference.

		if ( $db_check_string ) {
			$queries = array();
			foreach ( $data as $col => $value ) {
				if ( ! empty( $value['db'] ) ) {
					if ( ! isset( $queries[ $value['charset'] ] ) ) {
						$queries[ $value['charset'] ] = array();
					}

					// We're going to need to truncate by characters or bytes, depending on the length value we have.
					if ( 'byte' === $value['length']['type'] ) {
						// Split the CONVERT() calls by charset, so we can make sure the connection is right
						$queries[ $value['charset'] ][ $col ] = $this->prepare( "CONVERT( LEFT( CONVERT( %s USING binary ), %d ) USING {$value['charset']} )", $value['value'], $value['length']['length'] );
					} else {
						$queries[ $value['charset'] ][ $col ] = $this->prepare( "LEFT( CONVERT( %s USING {$value['charset']} ), %d )", $value['value'], $value['length']['length'] );
					}

					unset( $data[ $col ]['db'] );
				}
			}

			$connection_charset = $this->charset;
			foreach ( $queries as $charset => $query ) {
				if ( ! $query ) {
					continue;
				}

				// Change the charset to match the string(s) we're converting
				if ( $charset !== $connection_charset ) {
					$connection_charset = $charset;
					$this->set_charset( $this->dbh, $charset );
				}

				$this->check_current_query = false;

				$sql = array();
				foreach ( $query as $column => $column_query ) {
					$sql[] = $column_query . " AS x_$column";
				}

				$row = $this->get_row( "SELECT " . implode( ', ', $sql ), ARRAY_A );
				if ( ! $row ) {
					$this->set_charset( $this->dbh, $connection_charset );
					return new WP_Error( 'wpdb_strip_invalid_text_failure' );
				}

				foreach ( array_keys( $query ) as $column ) {
					$data[ $column ]['value'] = $row["x_$column"];
				}
			}

			// Don't forget to change the charset back!
			if ( $connection_charset !== $this->charset ) {
				$this->set_charset( $this->dbh );
			}
		}

		return $data;
	}

	/**
	 * Strips any invalid characters from the query.
	 *
	 * @since 4.2.0
	 * @access protected
	 *
	 * @param string $query Query to convert.
	 * @return string|WP_Error The converted query, or a {@see WP_Error} object if the conversion fails.
	 */
	protected function strip_invalid_text_from_query( $query ) {
		// We don't need to check the collation for queries that don't read data.
		$trimmed_query = ltrim( $query, "\r\n\t (" );
		if ( preg_match( '/^(?:SHOW|DESCRIBE|DESC|EXPLAIN|CREATE)\s/i', $trimmed_query ) ) {
			return $query;
		}

		$table = $this->get_table_from_query( $query );
		if ( $table ) {
			$charset = $this->get_table_charset( $table );
			if ( is_wp_error( $charset ) ) {
				return $charset;
			}

			// We can't reliably strip text from tables containing binary/blob columns
			if ( 'binary' === $charset ) {
				return $query;
			}
		} else {
			$charset = $this->charset;
		}

		$data = array(
			'value'   => $query,
			'charset' => $charset,
			'ascii'   => false,
			'length'  => false,
		);

		$data = $this->strip_invalid_text( array( $data ) );
		if ( is_wp_error( $data ) ) {
			return $data;
		}

		return $data[0]['value'];
	}

	/**
	 * Strips any invalid characters from the string for a given table and column.
	 *
	 * @since 4.2.0
	 * @access public
	 *
	 * @param string $table  Table name.
	 * @param string $column Column name.
	 * @param string $value  The text to check.
	 * @return string|WP_Error The converted string, or a `WP_Error` object if the conversion fails.
	 */
	public function strip_invalid_text_for_column( $table, $column, $value ) {
		if ( ! is_string( $value ) ) {
			return $value;
		}

		$charset = $this->get_col_charset( $table, $column );
		if ( ! $charset ) {
			// Not a string column.
			return $value;
		} elseif ( is_wp_error( $charset ) ) {
			// Bail on real errors.
			return $charset;
		}

		$data = array(
			$column => array(
				'value'   => $value,
				'charset' => $charset,
				'length'  => $this->get_col_length( $table, $column ),
			)
		);

		$data = $this->strip_invalid_text( $data );
		if ( is_wp_error( $data ) ) {
			return $data;
		}

		return $data[ $column ]['value'];
	}

	/**
	 * Find the first table name referenced in a query.
	 *
	 * @since 4.2.0
	 * @access protected
	 *
	 * @param string $query The query to search.
	 * @return string|false $table The table name found, or false if a table couldn't be found.
	 */
	protected function get_table_from_query( $query ) {
		// Remove characters that can legally trail the table name.
		$query = rtrim( $query, ';/-#' );

		// Allow (select...) union [...] style queries. Use the first query's table name.
		$query = ltrim( $query, "\r\n\t (" );

		/*
		 * Strip everything between parentheses except nested selects and use only 1,000
		 * chars of the query.
		 */
		$query = preg_replace( '/\((?!\s*select)[^(]*?\)/is', '()', substr( $query, 0, 1000 ) );

		// Quickly match most common queries.
		if ( preg_match( '/^\s*(?:'
				. 'SELECT.*?\s+FROM'
				. '|INSERT(?:\s+LOW_PRIORITY|\s+DELAYED|\s+HIGH_PRIORITY)?(?:\s+IGNORE)?(?:\s+INTO)?'
				. '|REPLACE(?:\s+LOW_PRIORITY|\s+DELAYED)?(?:\s+INTO)?'
				. '|UPDATE(?:\s+LOW_PRIORITY)?(?:\s+IGNORE)?'
				. '|DELETE(?:\s+LOW_PRIORITY|\s+QUICK|\s+IGNORE)*(?:\s+FROM)?'
				. ')\s+((?:[0-9a-zA-Z$_.`-]|[\xC2-\xDF][\x80-\xBF])+)/is', $query, $maybe ) ) {
			return str_replace( '`', '', $maybe[1] );
		}

		// SHOW TABLE STATUS and SHOW TABLES
		if ( preg_match( '/^\s*(?:'
				. 'SHOW\s+TABLE\s+STATUS.+(?:LIKE\s+|WHERE\s+Name\s*=\s*)'
				. '|SHOW\s+(?:FULL\s+)?TABLES.+(?:LIKE\s+|WHERE\s+Name\s*=\s*)'
				. ')\W((?:[0-9a-zA-Z$_.`-]|[\xC2-\xDF][\x80-\xBF])+)\W/is', $query, $maybe ) ) {
			return str_replace( '`', '', $maybe[1] );
		}

		// Big pattern for the rest of the table-related queries.
		if ( preg_match( '/^\s*(?:'
				. '(?:EXPLAIN\s+(?:EXTENDED\s+)?)?SELECT.*?\s+FROM'
				. '|DESCRIBE|DESC|EXPLAIN|HANDLER'
				. '|(?:LOCK|UNLOCK)\s+TABLE(?:S)?'
				. '|(?:RENAME|OPTIMIZE|BACKUP|RESTORE|CHECK|CHECKSUM|ANALYZE|REPAIR).*\s+TABLE'
				. '|TRUNCATE(?:\s+TABLE)?'
				. '|CREATE(?:\s+TEMPORARY)?\s+TABLE(?:\s+IF\s+NOT\s+EXISTS)?'
				. '|ALTER(?:\s+IGNORE)?\s+TABLE'
				. '|DROP\s+TABLE(?:\s+IF\s+EXISTS)?'
				. '|CREATE(?:\s+\w+)?\s+INDEX.*\s+ON'
				. '|DROP\s+INDEX.*\s+ON'
				. '|LOAD\s+DATA.*INFILE.*INTO\s+TABLE'
				. '|(?:GRANT|REVOKE).*ON\s+TABLE'
				. '|SHOW\s+(?:.*FROM|.*TABLE)'
				. ')\s+\(*\s*((?:[0-9a-zA-Z$_.`-]|[\xC2-\xDF][\x80-\xBF])+)\s*\)*/is', $query, $maybe ) ) {
			return str_replace( '`', '', $maybe[1] );
		}

		return false;
	}

	/**
	 * Load the column metadata from the last query.
	 *
	 * @since 3.5.0
	 *
	 * @access protected
	 */
	protected function load_col_info() {
		if ( $this->col_info )
			return;

		for ( $i = 0; $i < @mysql_num_fields( $this->result ); $i++ ) {
			$this->col_info[ $i ] = @mysql_fetch_field( $this->result, $i );
		}
	}

	/**
	 * Retrieve column metadata from the last query.
	 *
	 * @since 0.71
	 *
	 * @param string $info_type Optional. Type one of name, table, def, max_length, not_null, primary_key, multiple_key, unique_key, numeric, blob, type, unsigned, zerofill
	 * @param int $col_offset Optional. 0: col name. 1: which table the col's in. 2: col's max length. 3: if the col is numeric. 4: col's type
	 * @return mixed Column Results
	 */
	function get_col_info( $info_type = 'name', $col_offset = -1 ) {
		$this->load_col_info();

		if ( $this->col_info ) {
			if ( $col_offset == -1 ) {
				$i = 0;
				$new_array = array();
				foreach( (array) $this->col_info as $col ) {
					$new_array[$i] = $col->{$info_type};
					$i++;
				}
				return $new_array;
			} else {
				return $this->col_info[$col_offset]->{$info_type};
			}
		}
	}

	/**
	 * Starts the timer, for debugging purposes.
	 *
	 * @since 1.5.0
	 *
	 * @return true
	 */
	function timer_start() {
		$this->time_start = microtime( true );
		return true;
	}

	/**
	 * Stops the debugging timer.
	 *
	 * @since 1.5.0
	 *
	 * @return float Total time spent on the query, in seconds
	 */
	function timer_stop() {
		return ( microtime( true ) - $this->time_start );
	}

	/**
	 * Wraps errors in a nice header and footer and dies.
	 *
	 * Will not die if wpdb::$show_errors is false.
	 *
	 * @since 1.5.0
	 *
	 * @param string $message The Error message
	 * @param string $error_code Optional. A Computer readable string to identify the error.
	 * @return false|void
	 */
	function bail( $message, $error_code = '500' ) {
		if ( !$this->show_errors ) {
			if ( class_exists( 'WP_Error' ) )
				$this->error = new WP_Error($error_code, $message);
			else
				$this->error = $message;
			return false;
		}
		wp_die($message);
	}

	/**
	 * Whether MySQL database is at least the required minimum version.
	 *
	 * @since 2.5.0
	 * @uses $wp_version
	 * @uses $required_mysql_version
	 *
	 * @return WP_Error
	 */
	function check_database_version() {
		global $wp_version, $required_mysql_version;
		// Make sure the server has the required MySQL version
		if ( version_compare($this->db_version(), $required_mysql_version, '<') )
			return new WP_Error('database_version', sprintf( __( '<strong>ERROR</strong>: WordPress %1$s requires MySQL %2$s or higher' ), $wp_version, $required_mysql_version ));
	}

	/**
	 * Whether the database supports collation.
	 *
	 * Called when WordPress is generating the table scheme.
	 *
	 * @since 2.5.0
	 * @deprecated 3.5.0
	 * @deprecated Use wpdb::has_cap( 'collation' )
	 *
	 * @return bool True if collation is supported, false if version does not
	 */
	function supports_collation() {
		_deprecated_function( __FUNCTION__, '3.5', 'wpdb::has_cap( \'collation\' )' );
		return $this->has_cap( 'collation' );
	}

	/**
	 * The database character collate.
	 *
	 * @since 3.5.0
	 *
	 * @return string The database character collate.
	 */
	public function get_charset_collate() {
		$charset_collate = '';

		if ( ! empty( $this->charset ) )
			$charset_collate = "DEFAULT CHARACTER SET $this->charset";
		if ( ! empty( $this->collate ) )
			$charset_collate .= " COLLATE $this->collate";

		return $charset_collate;
	}

	/**
	 * Determine if a database supports a particular feature.
	 *
	 * @since 2.7.0
	 * @see wpdb::db_version()
	 *
	 * @param string $db_cap The feature to check for.
	 * @return bool
	 */
	function has_cap( $db_cap ) {
		$version = $this->db_version();

		switch ( strtolower( $db_cap ) ) {
			case 'collation' :    // @since 2.5.0
			case 'group_concat' : // @since 2.7.0
			case 'subqueries' :   // @since 2.7.0
				return version_compare( $version, '4.1', '>=' );
			case 'set_charset' :
				return version_compare( $version, '5.0.7', '>=' );
		};

		return false;
	}

	/**
	 * Retrieve the name of the function that called wpdb.
	 *
	 * Searches up the list of functions until it reaches
	 * the one that would most logically had called this method.
	 *
	 * @since 2.5.0
	 *
	 * @return string The name of the calling function
	 */
	function get_caller() {
		return wp_debug_backtrace_summary( __CLASS__ );
	}

	/**
	 * The database version number.
	 *
	 * @since 2.7.0
	 *
	 * @return false|string false on failure, version number on success
	 */
	function db_version() {
		return preg_replace( '/[^0-9.].*/', '', mysql_get_server_info( $this->dbh ) );
	}
}