apply_filters()　WordPress関数

<?php
143	/**
144	 * Calls the callback functions that have been added to a filter hook.
145	 *
146	 * The callback functions attached to the filter hook are invoked by calling
147	 * this function. This function can be used to create a new filter hook by
148	 * simply calling this function with the name of the new hook specified using
149	 * the `$tag` parameter.
150	 *
151	 * The function also allows for multiple additional arguments to be passed to hooks.
152	 *
153	 * Example usage:
154	 *
155	 *     // The filter callback function
156	 *     function example_callback( $string, $arg1, $arg2 ) {
157	 *         // (maybe) modify $string
158	 *         return $string;
159	 *     }
160	 *     add_filter( 'example_filter', 'example_callback', 10, 3 );
161	 *
162	 *     /*
163	 *      * Apply the filters by calling the 'example_callback()' function that's
164	 *      * hooked onto `example_filter` above.
165	 *      *
166	 *      * - 'example_filter' is the filter hook
167	 *      * - 'filter me' is the value being filtered
168	 *      * - $arg1 and $arg2 are the additional arguments passed to the callback.
169	 *     $value = apply_filters( 'example_filter', 'filter me', $arg1, $arg2 );
170	 *
171	 * @since 0.71
172	 *
173	 * @global array $wp_filter         Stores all of the filters.
174	 * @global array $wp_current_filter Stores the list of current filters with the current one last.
175	 *
176	 * @param string $tag     The name of the filter hook.
177	 * @param mixed  $value   The value to filter.
178	 * @param mixed  ...$args Additional parameters to pass to the callback functions.
179	 * @return mixed The filtered value after all hooked functions are applied to it.
180	 */
181	function apply_filters( $tag, $value ) {
182	        global $wp_filter, $wp_current_filter;
183	
184	        $args = func_get_args();
185	
186	        // Do 'all' actions first.
187	        if ( isset( $wp_filter['all'] ) ) {
188	                $wp_current_filter[] = $tag;
189	                _wp_call_all_hook( $args );
190	        }
191	
192	        if ( ! isset( $wp_filter[ $tag ] ) ) {
193	                if ( isset( $wp_filter['all'] ) ) {
194	                        array_pop( $wp_current_filter );
195	                }
196	                return $value;
197	        }
198	
199	        if ( ! isset( $wp_filter['all'] ) ) {
200	                $wp_current_filter[] = $tag;
201	        }
202	
203	        // Don't pass the tag name to WP_Hook.
204	        array_shift( $args );
205	
206	        $filtered = $wp_filter[ $tag ]->apply_filters( $value, $args );
207	
208	        array_pop( $wp_current_filter );
209	
210	        return $filtered;
211	}
?>