Database: Replace `substr_compare()` usage with `substr()` in `wpdb::prepare()`.

This amends the previous commit to avoid a warning on PHP < 7.2.18 if haystack is an empty string:
{{{
Warning: substr_compare(): The start position cannot exceed initial string length
}}}

Follow-up to [55151], [55157].

See #52506.
Built from https://develop.svn.wordpress.org/trunk@55158


git-svn-id: http://core.svn.wordpress.org/trunk@54691 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wpdb.php

@@ -1562,7 +1562,7 @@ class wpdb {
 			$type   = substr( $placeholder, -1 );
 
 			if ( 'f' === $type && true === $this->allow_unsafe_unquoted_parameters
-				&& 0 === substr_compare( $split_query[ $key - 1 ], '%', -1, 1 )
+				&& '%' === substr( $split_query[ $key - 1 ], -1, 1 )
 			) {
 
 				/*
@@ -1623,7 +1623,7 @@ class wpdb {
 					 * Second, if "%s" has a "%" before it, even if it's unrelated (e.g. "LIKE '%%%s%%'").
 					 */
 					if ( true !== $this->allow_unsafe_unquoted_parameters
-						|| ( '' === $format && 0 !== substr_compare( $split_query[ $key - 1 ], '%', -1, 1 ) )
+						|| ( '' === $format && '%' !== substr( $split_query[ $key - 1 ], -1, 1 ) )
 					) {
 						$placeholder = "'%" . $format . "s'";
 					}

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.2-alpha-55157';
+$wp_version = '6.2-alpha-55158';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.