4 * Hooks a function to a specific filter action.
6 * Filters are the hooks that WordPress launches to modify text of various types
7 * before adding it to the database or sending it to the browser screen. Plugins
8 * can specify that one or more of its PHP functions is executed to
9 * modify specific types of text at these times, using the Filter API.
10 * See the [Plugin API] for a list of filter hooks.
12 * @param string $tag The name of the filter to hook the <tt>$function_to_add</tt> to.
13 * @param callback $function_to_add The name of the function to be called when the filter is applied.
14 * @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.
15 * @param int $accepted_args optional. The number of arguments the function accept (default 1). In WordPress 1.5.1+, hooked functions can take extra arguments that are set when the matching do_action() or apply_filters() call is run.
16 * @return boolean true if the <tt>$function_to_add</tt> is added succesfully to filter <tt>$tag</tt>. How many arguments your function takes. In WordPress 1.5.1+, hooked functions can take extra arguments that are set when the matching <tt>do_action()</tt> or <tt>apply_filters()</tt> call is run. For example, the action <tt>comment_id_not_found</tt> will pass any functions that hook onto it the ID of the requested comment.
18 function add_filter($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
19 global $wp_filter, $merged_filters;
21 // So the format is wp_filter['tag']['array of priorities']['array of functions serialized']['array of ['array (functions, accepted_args)]']
22 $idx = _wp_filter_build_unique_id($tag, $function_to_add, $priority);
23 $wp_filter[$tag][$priority][$idx] = array('function' => $function_to_add, 'accepted_args' => $accepted_args);
24 //$wp_filter[$tag][$priority][serialize($function_to_add)] = array('function' => $function_to_add, 'accepted_args' => $accepted_args);
25 unset( $merged_filters[ $tag ] );
30 * Call the functions added to a filter hook.
32 * The callback functions attached to filter hook <tt>$tag</tt> are invoked by
33 * calling this function. This function can be used to create a new filter hook
34 * by simply calling this function with the name of the new hook specified using
35 * the <tt>$tag</a> parameter.
36 * @uses merge_filters Merges the filter hooks using this function.
37 * @param string $tag The name of the filter hook.
38 * @param string $string The text on which the filters hooked to <tt>$tag</tt> are applied on.
39 * @param mixed $var,... Additional variables passed to the functions hooked to <tt>$tag</tt>.
40 * @return string The text in <tt>$string</tt> after all hooked functions are applied to it.
42 function apply_filters($tag, $string) {
43 global $wp_filter, $merged_filters;
45 if ( !isset( $merged_filters[ $tag ] ) )
48 if ( !isset($wp_filter[$tag]) )
51 reset( $wp_filter[ $tag ] );
53 $args = func_get_args();
56 foreach( (array) current($wp_filter[$tag]) as $the_ )
57 if ( !is_null($the_['function']) ){
59 $string = call_user_func_array($the_['function'], array_slice($args, 1, (int) $the_['accepted_args']));
62 } while ( next($wp_filter[$tag]) !== false );
68 * Merge the filter functions of a specific filter hook with generic filter functions.
70 * It is possible to defined generic filter functions using the filter hook
71 * <em>all</e>. These functions are called for every filter tag. This function
72 * merges the functions attached to the <em>all</em> hook with the functions
73 * of a specific hoook defined by <tt>$tag</tt>.
74 * @param string $tag The filter hook of which the functions should be merged.
76 function merge_filters($tag) {
77 global $wp_filter, $merged_filters;
79 if ( isset($wp_filter['all']) && is_array($wp_filter['all']) )
80 $wp_filter[$tag] = array_merge($wp_filter['all'], (array) $wp_filter[$tag]);
82 if ( isset($wp_filter[$tag]) ){
83 reset($wp_filter[$tag]);
84 uksort($wp_filter[$tag], "strnatcasecmp");
86 $merged_filters[ $tag ] = true;
90 * Removes a function from a specified filter hook.
92 * This function removes a function attached to a specified filter hook. This
93 * method can be used to remove default functions attached to a specific filter
94 * hook and possibly replace them with a substitute.
95 * @param string $tag The filter hook to which the function to be removed is hooked.
96 * @param callback $function_to_remove The name of the function which should be removed.
97 * @param int $priority optional. The priority of the function (default: 10).
98 * @param int $accepted_args optional. The number of arguments the function accpets (default: 1).
99 * @return boolean Whether the function is removed.
101 function remove_filter($tag, $function_to_remove, $priority = 10, $accepted_args = 1) {
102 $function_to_remove = _wp_filter_build_unique_id($tag, $function_to_remove, $priority);
104 $r = isset($GLOBALS['wp_filter'][$tag][$priority][$function_to_remove]);
106 unset($GLOBALS['wp_filter'][$tag][$priority][$function_to_remove]);
107 unset($GLOBALS['merged_filters'][$tag]);
113 * Hooks a function on to a specific action.
115 * Actions are the hooks that the WordPress core launches at specific points
116 * during execution, or when specific events occur. Plugins can specify that
117 * one or more of its PHP functions are executed at these points, using the
120 * @param string $tag The name of the action to which the <tt>$function_to-add</tt> is hooked.
121 * @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.
122 * @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.
123 * @param int $accepted_args optional. The number of arguments the function accept (default 1). In WordPress 1.5.1+, hooked functions can take extra arguments that are set when the matching do_action() or apply_filters() call is run.
124 * @return boolean Always true.
126 function add_action($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
127 add_filter($tag, $function_to_add, $priority, $accepted_args);
131 * Execute functions hooked on a specific action hook.
133 * This function invokes all functions attached to action hook <tt>$tag</tt>.
134 * It is possible to create new action hooks by simply calling this function,
135 * specifying the name of the new hook using the <tt>$tag</tt> parameter.
136 * @uses merge_filters
137 * @param string $tag The name of the action to be executed.
138 * @param mixed $arg,... Optional additional arguments which are passed on to the functions hooked to the action.
140 function do_action($tag, $arg = '') {
141 global $wp_filter, $wp_actions;
143 if ( is_array($wp_actions) )
144 $wp_actions[] = $tag;
146 $wp_actions = array($tag);
149 if ( is_array($arg) && 1 == count($arg) && is_object($arg[0]) ) // array(&$this)
153 for ( $a = 2; $a < func_num_args(); $a++ )
154 $args[] = func_get_arg($a);
158 if ( !isset($wp_filter[$tag]) )
162 foreach( (array) current($wp_filter[$tag]) as $the_ )
163 if ( !is_null($the_['function']) )
164 call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));
166 } while ( next($wp_filter[$tag]) !== false );
171 * Return the number times an action is fired.
172 * @param string $tag The name of the action hook.
173 * @return int The number of times action hook <tt>$tag</tt> is fired
175 function did_action($tag) {
178 if ( empty($wp_actions) )
181 return count(array_keys($wp_actions, $tag));
185 * Execute functions hooked on a specific action hook, specifying arguments in a array.
187 * This function is identical to {@link do_action}, but the argumetns passe to
188 * the functions hooked to <tt>$tag</tt> are supplied using an array.
189 * @param string $tag The name of the action to be executed.
190 * @param array $args The arguments supplied to the functions hooked to <tt>$tag</tt>
192 function do_action_ref_array($tag, $args) {
193 global $wp_filter, $wp_actions;
195 if ( !is_array($wp_actions) )
196 $wp_actions = array($tag);
198 $wp_actions[] = $tag;
202 if ( !isset($wp_filter[$tag]) )
206 foreach( (array) current($wp_filter[$tag]) as $the_ )
207 if ( !is_null($the_['function']) )
208 call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));
210 } while ( next($wp_filter[$tag]) !== false );
215 * Removes a function from a specified action hook.
217 * This function removes a function attached to a specified action hook. This
218 * method can be used to remove default functions attached to a specific filter
219 * hook and possibly replace them with a substitute.
220 * @param string $tag The action hook to which the function to be removed is hooked.
221 * @param callback $function_to_remove The name of the function which should be removed.
222 * @param int $priority optional The priority of the function (default: 10).
223 * @param int $accepted_args optional. The number of arguments the function accpets (default: 1).
224 * @return boolean Whether the function is removed.
226 function remove_action($tag, $function_to_remove, $priority = 10, $accepted_args = 1) {
227 return remove_filter($tag, $function_to_remove, $priority, $accepted_args);
231 // Functions for handling plugins.
235 * Gets the basename of a plugin.
237 * This method extract the name of a plugin from its filename.
238 * @param string $file The filename of plugin.
239 * @return string The name of a plugin.
241 function plugin_basename($file) {
242 $file = str_replace('\\','/',$file); // sanitize for Win32 installs
243 $file = preg_replace('|/+|','/', $file); // remove any duplicate slash
244 $file = preg_replace('|^.*/wp-content/plugins/|','',$file); // get relative path from plugins dir
249 * Hook a function on a plugin activation action hook.
251 * When a plugin is activated, the action 'activate_PLUGINNAME' hook is
252 * activated. In the name of this hook, PLUGINNAME is replaced with the name of
253 * the plugin, including the optional subdirectory. For example, when the plugin
254 * is located in <tt>wp-content/plugin/sampleplugin/sample.php</tt>, then the
255 * name of this hook will become 'activate_sampleplugin/sample.php'.
256 * When the plugin consists of only one file and is (as by default) located at
257 * <tt>wp-content/plugin/sample.php</tt> the name of this hook will be
258 * 'activate_sample.php'.
259 * @param string $file The filename of the plugin including the path.
260 * @param string $function the function hooked to the 'activate_PLUGIN' action.
262 function register_activation_hook($file, $function) {
263 $file = plugin_basename($file);
264 add_action('activate_' . $file, $function);
268 * Hook a function on a plugin deactivation action hook.
270 * When a plugin is deactivated, the action 'deactivate_PLUGINNAME' hook is
271 * deactivated. In the name of this hook, PLUGINNAME is replaced with the name of
272 * the plugin, including the optional subdirectory. For example, when the plugin
273 * is located in <tt>wp-content/plugin/sampleplugin/sample.php</tt>, then the
274 * name of this hook will become 'activate_sampleplugin/sample.php'.
275 * When the plugin consists of only one file and is (as by default) located at
276 * <tt>wp-content/plugin/sample.php</tt> the name of this hook will be
277 * 'activate_sample.php'.
278 * @param string $file The filename of the plugin including the path.
279 * @param string $function the function hooked to the 'activate_PLUGIN' action.
281 function register_deactivation_hook($file, $function) {
282 $file = plugin_basename($file);
283 add_action('deactivate_' . $file, $function);
286 function _wp_filter_build_unique_id($tag, $function, $priority = 10)
290 // If function then just skip all of the tests and not overwrite the following.
292 if( is_string($function) )
294 // Object Class Calling
295 else if(is_object($function[0]) )
297 $obj_idx = get_class($function[0]).$function[1];
298 if( is_null($function[0]->wp_filter_id) ) {
299 $count = count((array)$wp_filter[$tag][$priority]);
300 $function[0]->wp_filter_id = $count;
304 $obj_idx .= $function[0]->wp_filter_id;
307 else if( is_string($function[0]) )
308 return $function[0].$function[1];