WordPress/wp-includes/plugin.php
2008-05-27 17:55:24 +00:00

600 lines
21 KiB
PHP

<?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
*/
/**
* 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.
*
* 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 $accepted_args optional. The number of arguments the function accept (default 1).
* @return boolean true
*/
function add_filter($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
global $wp_filter, $merged_filters;
$idx = _wp_filter_build_unique_id($tag, $function_to_add, $priority);
$wp_filter[$tag][$priority][$idx] = array('function' => $function_to_add, 'accepted_args' => $accepted_args);
unset( $merged_filters[ $tag ] );
return true;
}
/**
* 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>$tag</a> parameter.
*
* The function allows for additional arguments to be added and passed to hooks.
* <code>
* function example_hook($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 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 mixed The filtered value after all hooked functions are applied to it.
*/
function apply_filters($tag, $value) {
global $wp_filter, $merged_filters, $wp_current_filter;
$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]) ) {
array_pop($wp_current_filter);
return $value;
}
// Sort
if ( !isset( $merged_filters[ $tag ] ) ) {
ksort($wp_filter[$tag]);
$merged_filters[ $tag ] = true;
}
reset( $wp_filter[ $tag ] );
if ( empty($args) )
$args = func_get_args();
do {
foreach( (array) current($wp_filter[$tag]) as $the_ )
if ( !is_null($the_['function']) ){
$args[1] = $value;
$value = call_user_func_array($the_['function'], array_slice($args, 1, (int) $the_['accepted_args']));
}
} while ( next($wp_filter[$tag]) !== false );
array_pop( $wp_current_filter );
return $value;
}
/**
* remove_filter() - Removes a function from a specified filter hook.
*
* This function removes a function attached to a specified filter hook. This
* method can be used to remove default functions attached to a specific filter
* hook and possibly replace them with a substitute.
*
* To remove a hook, the <tt>$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 $accepted_args optional. The number of arguments the function accpets (default: 1).
* @return boolean Whether the function existed before it was removed.
*/
function remove_filter($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]);
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;
}
/**
* 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.
* @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 $accepted_args optional. The number of arguments the function accept (default 1).
*/
function add_action($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
return add_filter($tag, $function_to_add, $priority, $accepted_args);
}
/**
* do_action() - Execute functions hooked on a specific action hook.
*
* This function invokes all functions attached to action hook <tt>$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.
*
* 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, $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];
else
$args[] = $arg;
for ( $a = 2; $a < func_num_args(); $a++ )
$args[] = func_get_arg($a);
// 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);
}
/**
* 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
*/
function did_action($tag) {
global $wp_actions;
if ( empty($wp_actions) )
return 0;
return count(array_keys($wp_actions, $tag));
}
/**
* do_action_ref_array() - Execute functions hooked on a specific action hook, specifying arguments in an array.
*
* @see do_action() This function is identical, but the arguments passed to
* the functions hooked to <tt>$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, $merged_filters, $wp_current_filter;
if ( !is_array($wp_actions) )
$wp_actions = array($tag);
else
$wp_actions[] = $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;
}
// 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);
}
/**
* 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).
* @param int $accepted_args optional. The number of arguments the function accpets (default: 1).
* @return boolean Whether the function is removed.
*/
function remove_action($tag, $function_to_remove, $priority = 10, $accepted_args = 1) {
return remove_filter($tag, $function_to_remove, $priority, $accepted_args);
}
//
// Functions for handling plugins.
//
/**
* plugin_basename() - Gets the basename of a plugin.
*
* This method extracts the name of a plugin from its filename.
*
* @package WordPress
* @subpackage Plugin
* @since 1.5
*
* @access private
*
* @param string $file The filename of plugin.
* @return string The name of a plugin.
* @uses WP_PLUGIN_DIR
*/
function plugin_basename($file) {
$file = str_replace('\\','/',$file); // sanitize for Win32 installs
$file = preg_replace('|/+|','/', $file); // remove any duplicate slash
$plugin_dir = str_replace('\\','/',WP_PLUGIN_DIR); // sanitize for Win32 installs
$plugin_dir = preg_replace('|/+|','/', $plugin_dir); // remove any duplicate slash
$file = preg_replace('|^' . preg_quote($plugin_dir, '|') . '/|','',$file); // get relative path from plugins dir
return $file;
}
/**
* 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'
* 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 $function the function hooked to the 'activate_PLUGIN' action.
*/
function register_activation_hook($file, $function) {
$file = plugin_basename($file);
add_action('activate_' . $file, $function);
}
/**
* 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
* 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'.
* 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 $function the function hooked to the 'activate_PLUGIN' action.
*/
function register_deactivation_hook($file, $function) {
$file = plugin_basename($file);
add_action('deactivate_' . $file, $function);
}
/**
* _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 $wp_filter;
// If function then just skip all of the tests and not overwrite the following.
if ( is_string($function) )
return $function;
// Object Class Calling
else if (is_object($function[0]) ) {
$obj_idx = get_class($function[0]).$function[1];
if ( !isset($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 .= $count;
unset($count);
} else
$obj_idx .= $function[0]->wp_filter_id;
return $obj_idx;
}
// Static Calling
else if ( is_string($function[0]) )
return $function[0].$function[1];
}
?>