Merged with WordPress 2.5, unstable, only for testing

git-svn-id: http://svn.automattic.com/wordpress-mu/trunk@1218 7be80a69-a1ef-0310-a953-fb0f7c49ff36

1 files changed, 366 insertions, 82 deletions

diff --git a/wp-includes/plugin.php b/wp-includes/plugin.php
index 26b79ca..556570a 100644
--- a/wp-includes/plugin.php
+++ b/wp-includes/plugin.php
@@ -1,150 +1,294 @@
 <?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.
+ *
+ * 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.
+ * add_filter() - 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 0.71
+ * @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 $accepted_args optional. The number of arguments the function accept (default 1). In WordPress 1.5.1+, hooked functions can take extra arguments that are set when the matching do_action() or apply_filters() call is run.
- * @return boolean true if the <tt>$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.
+ * @param int $accepted_args optional. The number of arguments the function accept (default 1).
+ * @return boolean true
  */
 function add_filter($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);
+	$wp_filter[$tag][$priority][$idx] = array('function' => $function_to_add, 'accepted_args' => $accepted_args);
 	unset( $merged_filters[ $tag ] );
 	return true;
 }
 
 /**
- * Call the functions added to a filter hook.
+ * has_filter() - Check if any filter has been registered for a hook.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 2.5
+ * @global array $wp_filter Stores all of the filters
+ *
+ * @param string $tag The name of the filter hook.
+ * @param callback $function_to_check optional.  If specified, return the priority of that function on this hook or false if not attached.
+ * @return int|boolean Optionally returns the priority on that hook for the specified function.
+ */
+function has_filter($tag, $function_to_check = false) {
+	global $wp_filter;
+
+	$has = !empty($wp_filter[$tag]);
+	if ( false === $function_to_check || false == $has )
+		return $has;
+
+	if ( !$idx = _wp_filter_build_unique_id($tag, $function_to_check, false) )
+		return false;
+
+	foreach ( array_keys($wp_filter[$tag]) as $priority ) {
+		if ( isset($wp_filter[$tag][$priority][$idx]) )
+			return $priority;
+	}
+
+	return false;
+}
+
+/**
+ * apply_filters() - Call the functions added to a filter hook.
  *
  * The callback functions attached to filter hook <tt>$tag</tt> are invoked by
  * 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
+ *		return $string;
+ * }
+ * $value = apply_filters('example_filter', 'filter me', 'arg1', 'arg2');
+ * </code>
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 0.71
+ * @global array $wp_filter Stores all of the filters
+ * @global array $merge_filters Merges the filter hooks using this function.
+ * @global array $wp_current_filter stores the list of current filters with the current one last
+ *
  * @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 mixed $value The value on which the filters hooked to <tt>$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>$string</tt> after all hooked functions are applied to it.
+ * @return mixed The filtered value after all hooked functions are applied to it.
  */
-function apply_filters($tag, $string) {
-	global $wp_filter, $merged_filters;
+function apply_filters($tag, $value) {
+	global $wp_filter, $merged_filters, $wp_current_filter;
 
-	if ( !isset( $merged_filters[ $tag ] ) )
-		merge_filters($tag);
+	$args = array();
+	$wp_current_filter[] = $tag;
+
+	// Do 'all' actions first
+	if ( isset($wp_filter['all']) ) {
+		$args = func_get_args();
+		_wp_call_all_hook($args);
+	}
 
-	if ( !isset($wp_filter[$tag]) )
-		return $string;
+	if ( !isset($wp_filter[$tag]) ) {
+		array_pop($wp_current_filter);
+		return $value;
+	}
+
+	// Sort
+	if ( !isset( $merged_filters[ $tag ] ) ) {
+		ksort($wp_filter[$tag]);
+		$merged_filters[ $tag ] = true;
+	}
 
 	reset( $wp_filter[ $tag ] );
 
-	$args = func_get_args();
+	if ( empty($args) )
+		$args = func_get_args();
 
-	do{
+	do {
 		foreach( (array) current($wp_filter[$tag]) as $the_ )
 			if ( !is_null($the_['function']) ){
-				$args[1] = $string;
-				$string = call_user_func_array($the_['function'], array_slice($args, 1, (int) $the_['accepted_args']));
+				$args[1] = $value;
+				$value = call_user_func_array($the_['function'], array_slice($args, 1, (int) $the_['accepted_args']));
 			}
 
 	} while ( next($wp_filter[$tag]) !== false );
 
-	return $string;
-}
-
-/**
- * Merge the filter functions of a specific filter hook with generic filter functions.
- *
- * It is possible to defined generic filter functions using the filter hook
- * <em>all</e>. These functions are called for every filter tag. This function
- * merges the functions attached to the <em>all</em> hook with the functions
- * of a specific hoook defined by <tt>$tag</tt>.
- * @param string $tag The filter hook of which the functions should be merged.
- */
-function merge_filters($tag) {
-	global $wp_filter, $merged_filters;
-
-	if ( isset($wp_filter['all']) && is_array($wp_filter['all']) )
-		$wp_filter[$tag] = array_merge($wp_filter['all'], (array) $wp_filter[$tag]);
+	array_pop( $wp_current_filter );
 
-	if ( isset($wp_filter[$tag]) ){
-		reset($wp_filter[$tag]);
-		uksort($wp_filter[$tag], "strnatcasecmp");
-	}
-	$merged_filters[ $tag ] = true;
+	return $value;
 }
 
 /**
- * Removes a function from a specified filter hook.
+ * remove_filter() - Removes a function from a specified filter hook.
  *
  * 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 1.2
+ *
  * @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);
 
 	$r = isset($GLOBALS['wp_filter'][$tag][$priority][$function_to_remove]);
 
-	unset($GLOBALS['wp_filter'][$tag][$priority][$function_to_remove]);
-	unset($GLOBALS['merged_filters'][$tag]);
+	if ( true === $r) {
+		unset($GLOBALS['wp_filter'][$tag][$priority][$function_to_remove]);
+		if ( empty($GLOBALS['wp_filter'][$tag][$priority]) )
+			unset($GLOBALS['wp_filter'][$tag][$priority]);
+		unset($GLOBALS['merged_filters'][$tag]);
+	}
 
 	return $r;
 }
 
+
 /**
- * Hooks a function on to a specific action.
+ * current_filter() - Return the name of the current filter or action.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 2.5
+ *
+ * @return string Hook name of the current filter or action.
+ */
+function current_filter() {
+	global $wp_current_filter;
+	return end( $wp_current_filter );
+}
+
+
+/**
+ * add_action() - Hooks a function on to a specific action.
  *
  * Actions are the hooks that the WordPress core launches at specific points
  * during execution, or when specific events occur. Plugins can specify that
  * 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 1.2
+ *
  * @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.
- * @return boolean Always true.
+ * @param int $accepted_args optional. The number of arguments the function accept (default 1).
  */
 function add_action($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
-	add_filter($tag, $function_to_add, $priority, $accepted_args);
+	return add_filter($tag, $function_to_add, $priority, $accepted_args);
 }
 
+
 /**
- * Execute functions hooked on a specific action hook.
+ * do_action() - Execute functions hooked on a specific action hook.
  *
  * 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 1.2
+ * @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;
+	global $wp_filter, $wp_actions, $merged_filters, $wp_current_filter;
 
 	if ( is_array($wp_actions) )
 		$wp_actions[] = $tag;
 	else
 		$wp_actions = array($tag);
 
+	$wp_current_filter[] = $tag;
+
+	// Do 'all' actions first
+	if ( isset($wp_filter['all']) ) {
+		$all_args = func_get_args();
+		_wp_call_all_hook($all_args);
+	}
+
+	if ( !isset($wp_filter[$tag]) ) {
+		array_pop($wp_current_filter);
+		return;
+	}
+
 	$args = array();
 	if ( is_array($arg) && 1 == count($arg) && is_object($arg[0]) ) // array(&$this)
 		$args[] =& $arg[0];
@@ -153,22 +297,32 @@ function do_action($tag, $arg = '') {
 	for ( $a = 2; $a < func_num_args(); $a++ )
 		$args[] = func_get_arg($a);
 
-	merge_filters($tag);
+	// Sort
+	if ( !isset( $merged_filters[ $tag ] ) ) {
+		ksort($wp_filter[$tag]);
+		$merged_filters[ $tag ] = true;
+	}
 
-	if ( !isset($wp_filter[$tag]) )
-		return;
+	reset( $wp_filter[ $tag ] );
 
-	do{
-		foreach( (array) current($wp_filter[$tag]) as $the_ )
+	do {
+		foreach ( (array) current($wp_filter[$tag]) as $the_ )
 			if ( !is_null($the_['function']) )
 				call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));
 
 	} while ( next($wp_filter[$tag]) !== false );
 
+	array_pop($wp_current_filter);
 }
 
 /**
- * Return the number times an action is fired.
+ * did_action() - 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
  */
@@ -182,41 +336,87 @@ function did_action($tag) {
 }
 
 /**
- * Execute functions hooked on a specific action hook, specifying arguments in a array.
+ * do_action_ref_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.
+ *
+ * @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;
+	global $wp_filter, $wp_actions, $merged_filters, $wp_current_filter;
 
 	if ( !is_array($wp_actions) )
 		$wp_actions = array($tag);
 	else
 		$wp_actions[] = $tag;
 
-	merge_filters($tag);
+	$wp_current_filter[] = $tag;
+
+	// Do 'all' actions first
+	if ( isset($wp_filter['all']) ) {
+		$all_args = func_get_args();
+		_wp_call_all_hook($all_args);
+	}
 
-	if ( !isset($wp_filter[$tag]) )
+	if ( !isset($wp_filter[$tag]) ) {
+		array_pop($wp_current_filter);
 		return;
+	}
 
-	do{
+	// Sort
+	if ( !isset( $merged_filters[ $tag ] ) ) {
+		ksort($wp_filter[$tag]);
+		$merged_filters[ $tag ] = true;
+	}
+
+	reset( $wp_filter[ $tag ] );
+
+	do {
 		foreach( (array) current($wp_filter[$tag]) as $the_ )
 			if ( !is_null($the_['function']) )
 				call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));
 
 	} while ( next($wp_filter[$tag]) !== false );
 
+	array_pop($wp_current_filter);
+}
+
+/**
+ * has_action() - Check if any action has been registered for a hook.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 2.5
+ * @see has_filter() has_action() is an alias of has_filter().
+ *
+ * @param string $tag The name of the action hook.
+ * @param callback $function_to_check optional.  If specified, return the priority of that function on this hook or false if not attached.
+ * @return int|boolean Optionally returns the priority on that hook for the specified function.
+ */
+function has_action($tag, $function_to_check = false) {
+	return has_filter($tag, $function_to_check);
 }
 
 /**
- * Removes a function from a specified action hook.
+ * remove_action() - Removes a function from a specified action hook.
  *
  * 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.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 1.2
+ *
  * @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 $priority optional The priority of the function (default: 10).
@@ -232,31 +432,44 @@ function remove_action($tag, $function_to_remove, $priority = 10, $accepted_args
 //
 
 /**
- * Gets the basename of a plugin.
+ * plugin_basename() - 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 $file The filename of plugin.
  * @return string The name of a plugin.
  */
 function plugin_basename($file) {
 	$file = str_replace('\\','/',$file); // sanitize for Win32 installs
 	$file = preg_replace('|/+|','/', $file); // remove any duplicate slash
-	$file = preg_replace('|^.*/wp-content/plugins/|','',$file); // get relative path from plugins dir
-	$file = preg_replace('|^.*/wp-content/mu-plugins/|','',$file); // get relative path from mu-plugins dir
+	$file = preg_replace('|^.*/' . PLUGINDIR . '/|','',$file); // get relative path from plugins dir
 	return $file;
 }
 
 /**
- * Hook a function on a plugin activation action hook.
+ * register_activation_hook() - Hook a function on a plugin activation action hook.
  *
  * When a plugin is activated, the action 'activate_PLUGINNAME' hook is
  * 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 2.0
+ *
+ * @access private
+ *
  * @param string $file The filename of the plugin including the path.
  * @param string $function the function hooked to the 'activate_PLUGIN' action.
  */
@@ -266,7 +479,7 @@ function register_activation_hook($file, $function) {
 }
 
 /**
- * Hook a function on a plugin deactivation action hook.
+ * register_deactivation_hook() - Hook a function on a plugin deactivation action hook.
  *
  * When a plugin is deactivated, the action 'deactivate_PLUGINNAME' hook is
  * deactivated. In the name of this hook, PLUGINNAME is replaced with the name of
@@ -276,6 +489,13 @@ 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 $function the function hooked to the 'activate_PLUGIN' action.
  */
@@ -284,19 +504,82 @@ function register_deactivation_hook($file, $function) {
 	add_action('deactivate_' . $file, $function);
 }
 
-function _wp_filter_build_unique_id($tag, $function, $priority = 10)
-{
+/**
+ * _wp_call_all_hook() - Calls the 'all' hook, which will process the functions hooked into it.
+ *
+ * The 'all' hook passes all of the arguments or parameters that were used for the
+ * hook, which this function was called for.
+ *
+ * This function is used internally for apply_filters(), do_action(), and do_action_ref_array()
+ * and is not meant to be used from outside those functions. This function does not check for the
+ * existence of the all hook, so it will fail unless the all hook exists prior to this function call.
+ *
+ * @package WordPress
+ * @subpackage Plugin
+ * @since 2.5
+ * @access private
+ *
+ * @uses $wp_filter Used to process all of the functions in the 'all' hook
+ *
+ * @param array $args The collected parameters from the hook that was called.
+ * @param string $hook Optional. The hook name that was used to call the 'all' hook.
+ */
+function _wp_call_all_hook($args) {
+	global $wp_filter;
+
+	reset( $wp_filter['all'] );
+	do {
+		foreach( (array) current($wp_filter['all']) as $the_ )
+			if ( !is_null($the_['function']) )
+				call_user_func_array($the_['function'], $args);
+
+	} while ( next($wp_filter['all']) !== false );
+}
+
+/**
+ * _wp_filter_build_unique_id() - 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
+ *
+ * @global array $wp_filter Storage for all of the filters and actions
+ * @param string $tag Used in counting how many hooks were applied
+ * @param string|array $function Used for creating unique id
+ * @param int|bool $priority Used in counting how many hooks were applied.  If === false and $function is an object reference, we return the unique id only if it already has one, false otherwise.
+ * @param string $type filter or action
+ * @return string Unique ID for usage as array key
+ */
+function _wp_filter_build_unique_id($tag, $function, $priority) {
 	global $wp_filter;
 
 	// If function then just skip all of the tests and not overwrite the following.
-	// Static Calling
-	if( is_string($function) )
+	if ( is_string($function) )
 		return $function;
 	// Object Class Calling
-	else if(is_object($function[0]) )
-	{
+	else if (is_object($function[0]) ) {
 		$obj_idx = get_class($function[0]).$function[1];
-		if( is_null($function[0]->wp_filter_id) ) {
+		if ( !isset($function[0]->wp_filter_id) ) {
+			if ( false === $priority )
+				return false;
 			$count = count((array)$wp_filter[$tag][$priority]);
 			$function[0]->wp_filter_id = $count;
 			$obj_idx .= $count;
@@ -305,7 +588,8 @@ function _wp_filter_build_unique_id($tag, $function, $priority = 10)
 			$obj_idx .= $function[0]->wp_filter_id;
 		return $obj_idx;
 	}
-	else if( is_string($function[0]) )
+	// Static Calling
+	else if ( is_string($function[0]) )
 		return $function[0].$function[1];
 }