phpdoc for plugin API. Props darkdragon. fixes #5225

git-svn-id: http://svn.automattic.com/wordpress/trunk@6276 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/plugin.php

@@ -1,27 +1,79 @@
 <?php
+/**
+ * The plugin API is located in this file, which allows for creating actions
+ * and filters and hooking functions, and methods. The functions or methods will
+ * then be run when the action or filter is called.
+ *
+ * The API callback examples reference functions, but can be methods of classes.
+ * To hook methods, you'll need to pass an array one of two ways.
+ *
+ * For static methods (you won't have access to the <tt>$this</tt> variable in the
+ * method):
+ * <code>array('class_name', 'method_name');</code>
+ *
+ * The second method will need the reference to the object to have access to the
+ * method.
+ * <code>array(&$this, 'method_name');</code>
+ * <code>
+ * $obj = new myObject();
+ * array(&$obj, 'method_name');
+ * </code>
+ * Any of the syntaxes explained in the PHP documentation for the
+ * {@link http://us2.php.net/manual/en/language.pseudo-types.php#language.types.callback 'callback' type} are valid.
+ *
+ * Also see the {@link http://codex.wordpress.org/Plugin_API Plugin API} for more information
+ * and examples on how to use a lot of these functions.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 1.5
+ */
 
 /**
- * Hooks a function to a specific filter action.
+ * Hooks a function or method to a specific filter action.
  *
  * Filters are the hooks that WordPress launches to modify text of various types
  * before adding it to the database or sending it to the browser screen. Plugins
  * can specify that one or more of its PHP functions is executed to
  * modify specific types of text at these times, using the Filter API.
- * See the [Plugin API] for a list of filter hooks.
+ *
+ * To use the API, the following code should be used to bind a callback to the filter
+ * <code>
+ * function example_hook($example) { echo $example; }
+ *
+ * add_filter('example_filter', 'example_hook');
+ * </code>
+ *
+ * In WordPress 1.5.1+, hooked functions can take extra arguments that are set when
+ * the matching do_action() or apply_filters() call is run. The <tt>$accepted_args
+ * allow for calling functions only when the number of args match. Hooked functions
+ * can take extra arguments that are set when the matching <tt>do_action()</tt> or
+ * <tt>apply_filters()</tt> call is run. For example, the action <tt>comment_id_not_found</tt>
+ * will pass any functions that hook onto it the ID of the requested comment.
+ *
+ * <strong>Note:</strong> the function will return true no matter if the function was hooked
+ * fails or not. There are no checks for whether the function exists beforehand and no checks
+ * to whether the <tt>$function_to_add is even a string. It is up to you to take care and
+ * this is done for optimization purposes, so everything is as quick as possible.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 1.5
+ * @global array $wp_filter Stores all of the filters added in the form of
+ *	wp_filter['tag']['array of priorities']['array of functions serialized']['array of ['array (functions, accepted_args)]']
+ * @global array $merged_filters Tracks the tags that need to be merged for later. If the hook is added, it doesn't need to run through that process.
  *
  * @param string $tag The name of the filter to hook the <tt>$function_to_add</tt> to.
  * @param callback $function_to_add The name of the function to be called when the filter is applied.
  * @param int $priority optional. Used to specify the order in which the functions associated with a particular action are executed (default: 10). Lower numbers correspond with earlier execution, and functions with the same priority are executed in the order in which they were added to the action.
- * @param int $accepted_args optional. The number of arguments the function accept (default 1). In WordPress 1.5.1+, hooked functions can take extra arguments that are set when the matching do_action() or apply_filters() call is run.
+ * @param int $accepted_args optional. The number of arguments the function accept (default 1).
- * @return boolean true if the <tt>$function_to_add</tt> is added succesfully to filter <tt>$tag</tt>. How many arguments your function takes. In WordPress 1.5.1+, hooked functions can take extra arguments that are set when the matching <tt>do_action()</tt> or <tt>apply_filters()</tt> call is run. For example, the action <tt>comment_id_not_found</tt> will pass any functions that hook onto it the ID of the requested comment.
+ * @return boolean true
  */
 function add_filter($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
 	global $wp_filter, $merged_filters;
 
-	// So the format is wp_filter['tag']['array of priorities']['array of functions serialized']['array of ['array (functions, accepted_args)]']
 	$idx = _wp_filter_build_unique_id($tag, $function_to_add, $priority);
 	$wp_filter[$tag][$priority][$idx] = array('function' => $function_to_add, 'accepted_args' => $accepted_args);
-	//$wp_filter[$tag][$priority][serialize($function_to_add)] = array('function' => $function_to_add, 'accepted_args' => $accepted_args);
 	unset( $merged_filters[ $tag ] );
 	return true;
 }
@@ -33,20 +85,35 @@ function add_filter($tag, $function_to_add, $priority = 10, $accepted_args = 1)
  * calling this function. This function can be used to create a new filter hook
  * by simply calling this function with the name of the new hook specified using
  * the <tt>$tag</a> parameter.
- * @uses merge_filters Merges the filter hooks using this function.
+ *
+ * The function allows for additional arguments to be added and passed to hooks.
+ * <code>
+ * function example_hook($string, $arg1, $arg2)
+ * {
+ *		//Do stuff
+ * }
+ * $value = apply_filters('example_filter', 'filter me', 'arg1', 'arg2');
+ * </code>
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 1.5
+ * @global array $wp_filter Stores all of the filters
+ * @global array $merge_filters Merges the filter hooks using this function.
+ *
  * @param string $tag The name of the filter hook.
- * @param string $string The text on which the filters hooked to <tt>$tag</tt> are applied on.
+ * @param string $value The value on which the filters hooked to <tt>$tag</tt> are applied on.
  * @param mixed $var,... Additional variables passed to the functions hooked to <tt>$tag</tt>.
  * @return string The text in <tt>$string</tt> after all hooked functions are applied to it.
  */
-function apply_filters($tag, $string) {
+function apply_filters($tag, $value) {
 	global $wp_filter, $merged_filters;
 
 	if ( !isset( $merged_filters[ $tag ] ) )
 		merge_filters($tag);
 
 	if ( !isset($wp_filter[$tag]) )
-		return $string;
+		return $value;
 
 	reset( $wp_filter[ $tag ] );
 
@@ -55,13 +122,13 @@ function apply_filters($tag, $string) {
 	do{
 		foreach( (array) current($wp_filter[$tag]) as $the_ )
 			if ( !is_null($the_['function']) ){
-				$args[1] = $string;
+				$args[1] = $value;
-				$string = call_user_func_array($the_['function'], array_slice($args, 1, (int) $the_['accepted_args']));
+				$value = call_user_func_array($the_['function'], array_slice($args, 1, (int) $the_['accepted_args']));
 			}
 
 	} while ( next($wp_filter[$tag]) !== false );
 
-	return $string;
+	return $value;
 }
 
 /**
@@ -70,7 +137,17 @@ function apply_filters($tag, $string) {
  * It is possible to defined generic filter functions using the filter hook
  * <em>all</e>. These functions are called for every filter tag. This function
  * merges the functions attached to the <em>all</em> hook with the functions
- * of a specific hoook defined by <tt>$tag</tt>.
+ * of a specific hook defined by <tt>$tag</tt>.
+ *
+ * Bugged if you hook into 'all' tag, then you <strong>will</strong> lose all priority
+ * information. {@link http://trac.wordpress.org/ticket/4715 Bug #4715} for more information.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 1.5
+ * @global array $wp_filter Stores all of the filters
+ * @global array $merge_filters Merges the filter hooks using this function.
+ *
  * @param string $tag The filter hook of which the functions should be merged.
  */
 function merge_filters($tag) {
@@ -92,11 +169,20 @@ function merge_filters($tag) {
  * This function removes a function attached to a specified filter hook. This
  * method can be used to remove default functions attached to a specific filter
  * hook and possibly replace them with a substitute.
+ *
+ * To remove a hook, the <tt>$function_to_remove</tt> and <tt>$priority</tt> arguments
+ * must match when the hook was added. This goes for both filters and actions. No warning
+ * will be given on removal failure.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 1.5
+ *
  * @param string $tag The filter hook to which the function to be removed is hooked.
  * @param callback $function_to_remove The name of the function which should be removed.
  * @param int $priority optional. The priority of the function (default: 10).
  * @param int $accepted_args optional. The number of arguments the function accpets (default: 1).
- * @return boolean Whether the function is removed.
+ * @return boolean Whether the function existed before it was removed.
  */
 function remove_filter($tag, $function_to_remove, $priority = 10, $accepted_args = 1) {
 	$function_to_remove = _wp_filter_build_unique_id($tag, $function_to_remove, $priority);
@@ -117,11 +203,16 @@ function remove_filter($tag, $function_to_remove, $priority = 10, $accepted_args
  * one or more of its PHP functions are executed at these points, using the
  * Action API.
  *
+ * @uses add_filter() Adds an action. Parameter list and functionality are the same.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 1.5
+ *
  * @param string $tag The name of the action to which the <tt>$function_to-add</tt> is hooked.
- * @param callback $function_to_add The name of the function you wish to be called. Note: any of the syntaxes explained in the PHP documentation for the 'callback' type (http://us2.php.net/manual/en/language.pseudo-types.php#language.types.callback) are valid.
+ * @param callback $function_to_add The name of the function you wish to be called.
  * @param int $priority optional. Used to specify the order in which the functions associated with a particular action are executed (default: 10). Lower numbers correspond with earlier execution, and functions with the same priority are executed in the order in which they were added to the action.
- * @param int $accepted_args optional. The number of arguments the function accept (default 1). In WordPress 1.5.1+, hooked functions can take extra arguments that are set when the matching do_action() or apply_filters() call is run.
+ * @param int $accepted_args optional. The number of arguments the function accept (default 1).
- * @return boolean Always true.
  */
 function add_action($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
 	add_filter($tag, $function_to_add, $priority, $accepted_args);
@@ -133,9 +224,21 @@ function add_action($tag, $function_to_add, $priority = 10, $accepted_args = 1)
  * This function invokes all functions attached to action hook <tt>$tag</tt>.
  * It is possible to create new action hooks by simply calling this function,
  * specifying the name of the new hook using the <tt>$tag</tt> parameter.
- * @uses merge_filters
+ *
+ * You can pass extra arguments to the hooks, much like you can with apply_filters().
+ *
+ * @see apply_filters() This function works similar with the exception that nothing is
+ * returned and only the functions or methods are called.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 1.5
+ * @global array $wp_filter Stores all of the filters
+ * @global array $wp_actions Increments the amount of times action was triggered.
+ *
  * @param string $tag The name of the action to be executed.
  * @param mixed $arg,... Optional additional arguments which are passed on to the functions hooked to the action.
+ * @return null Will return null if $tag does not exist in $wp_filter array
  */
 function do_action($tag, $arg = '') {
 	global $wp_filter, $wp_actions;
@@ -169,6 +272,12 @@ function do_action($tag, $arg = '') {
 
 /**
  * Return the number times an action is fired.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 2.1
+ * @global array $wp_actions Increments the amount of times action was triggered.
+ *
  * @param string $tag The name of the action hook.
  * @return int The number of times action hook <tt>$tag</tt> is fired
  */
@@ -182,12 +291,22 @@ function did_action($tag) {
 }
 
 /**
- * Execute functions hooked on a specific action hook, specifying arguments in a array.
+ * Execute functions hooked on a specific action hook, specifying arguments in an array.
  *
- * This function is identical to {@link do_action}, but the argumetns passe to
+ * @see do_action() This function is identical, but the arguments passed to
  * the functions hooked to <tt>$tag</tt> are supplied using an array.
+ *
+ * @uses merge_filters()
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 2.1
+ * @global array $wp_filter Stores all of the filters
+ * @global array $wp_actions Increments the amount of times action was triggered.
+ *
  * @param string $tag The name of the action to be executed.
  * @param array $args The arguments supplied to the functions hooked to <tt>$tag</tt>
+ * @return null Will return null if $tag does not exist in $wp_filter array
  */
 function do_action_ref_array($tag, $args) {
 	global $wp_filter, $wp_actions;
@@ -217,6 +336,13 @@ function do_action_ref_array($tag, $args) {
  * This function removes a function attached to a specified action hook. This
  * method can be used to remove default functions attached to a specific filter
  * hook and possibly replace them with a substitute.
+ *
+ * @uses remove_filter() Uses remove_filter to remove actions added.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 1.5
+ *
  * @param string $tag The action hook to which the function to be removed is hooked.
  * @param callback $function_to_remove The name of the function which should be removed.
  * @param int $priority optional The priority of the function (default: 10).
@@ -235,6 +361,13 @@ function remove_action($tag, $function_to_remove, $priority = 10, $accepted_args
  * Gets the basename of a plugin.
  *
  * This method extract the name of a plugin from its filename.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 1.5
+ *
+ * @access private
+ *
  * @param string $file The filename of plugin.
  * @return string The name of a plugin.
  */
@@ -252,10 +385,17 @@ function plugin_basename($file) {
  * activated. In the name of this hook, PLUGINNAME is replaced with the name of
  * the plugin, including the optional subdirectory. For example, when the plugin
  * is located in <tt>wp-content/plugin/sampleplugin/sample.php</tt>, then the
- * name of this hook will become 'activate_sampleplugin/sample.php'.
+ * name of this hook will become 'activate_sampleplugin/sample.php'
  * When the plugin consists of only one file and is (as by default) located at
  * <tt>wp-content/plugin/sample.php</tt> the name of this hook will be
  * 'activate_sample.php'.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 1.5
+ *
+ * @access private
+ *
  * @param string $file The filename of the plugin including the path.
  * @param string $function the function hooked to the 'activate_PLUGIN' action.
  */
@@ -275,6 +415,13 @@ function register_activation_hook($file, $function) {
  * When the plugin consists of only one file and is (as by default) located at
  * <tt>wp-content/plugin/sample.php</tt> the name of this hook will be
  * 'activate_sample.php'.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 2.0
+ *
+ * @access private
+ *
  * @param string $file The filename of the plugin including the path.
  * @param string $function the function hooked to the 'activate_PLUGIN' action.
  */
@@ -284,27 +431,31 @@ function register_deactivation_hook($file, $function) {
 }
 
 /**
+ * Build Unique ID for storage and retrieval
+ *
+ * The old way to serialize the callback caused issues and this function is the
+ * solution. It works by checking for objects and creating an a new property in
+ * the class to keep track of the object and new objects of the same class that
+ * need to be added.
+ *
+ * It also allows for the removal of actions and filters for objects after they
+ * change class properties. It is possible to include the property $wp_filter_id
+ * in your class and set it to "null" or a number to bypass the workaround. However
+ * this will prevent you from adding new classes and any new classes will overwrite
+ * the previous hook by the same class.
+ *
+ * Functions and static method callbacks are just returned as strings and shouldn't
+ * have any speed penalty.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 2.2.3
+ *
+ * @link http://trac.wordpress.org/ticket/3875
+ *
  * @access private
  *
- * _wp_filter_build_unique_id() - Build Unique ID for storage and retrieval
+ * @global array $wp_filter Storage for all of the filters and actions
- *
- * This function is used to fix the issue where serialized, when used with 
- * classes that updated their properties, wouldn't be able to remove actions.
- *
- * How it works is that it first checks if the $function parameter is a string
- * and passes it through, untouched. Functions won't need to be changed, since
- * there can only be one declared.
- * 
- * The second type that will be passed through untouched, is for static methods
- * in classes. They don't need to be changed since they are much like functions
- * in that you can only call one of them.
- *
- * The main purpose of this function is for classes, which can have more than
- * one declared and you want to add more than one hook for each one that is 
- * declared, or want to change properties internal of the class that you declared
- * the hook.
- *
- * @global $wp_filter
  * @param string $tag Used in counting how many hooks were applied
  * @param string|array $function Used for creating unique id
  * @param int $priority Used in counting how many hooks were applied
@@ -315,14 +466,13 @@ function _wp_filter_build_unique_id($tag, $function, $priority = 10)
 	global $wp_filter;
 
 	// If function then just skip all of the tests and not overwrite the following.
-	// Static Calling
 	if( is_string($function) )
 		return $function;
 	// Object Class Calling
 	else if(is_object($function[0]) )
 	{
 		$obj_idx = get_class($function[0]).$function[1];
-		if( is_null($function[0]->wp_filter_id) ) {
+		if( is_null($function[0]->wp_filter_id) ) { // This should be instead of is_null() change to !isset() to fix notice
 			$count = count((array)$wp_filter[$tag][$priority]);
 			$function[0]->wp_filter_id = $count;
 			$obj_idx .= $count;
@@ -331,6 +481,7 @@ function _wp_filter_build_unique_id($tag, $function, $priority = 10)
 			$obj_idx .= $function[0]->wp_filter_id;
 		return $obj_idx;
 	}
+	// Static Calling
 	else if( is_string($function[0]) )
 		return $function[0].$function[1];
 }