WordPress Plugin Refactoring Example

EventStorageInterface.php

<?php

interface StorageInterface {

	public function listen( $name, $listener, $priority = 10, $limitArguments = 1 );

	public function hasListener( $name, $listener = null );

	public function silence( $name, $listener, $priority = 10 );

	public function silenceAll( $name, $priority = false );

	public function firing();

	public function listened( $name = null );

	public function fired( $name );

	public function apply( $name, $value, array $arguments );

	public function call( $name, array $arguments );
}

registry.php

<?php

function event_registry(EventStorageInterface $storage = null) {
	static $_storage = null;
	
	if ( is_object($storage) ) {
		$_storage = $storage;
	}
	
	if ( !is_object($_storage) ) {
		$_storage = new Default_Event_Storage;
	}
	
	return $_storage;
}

wp-plugin.php

<?php

function add_filter( $name, $listener, $priority = 10, $limitArguments = 1 ) {
	return event_registry()->listen( $name, $listener, $priority, $limitArguments );
}

function has_filter( $name, $listener = null ) {
	return event_registry()->hasListener( $name, $listener );
}

function apply_filters( $name, $value ) {
	$arguments = array();
	if (func_num_args() > 2) {
		$arguments = array_slice(func_get_args(), 2);
	}
	return event_registry()->apply( $name, $value, $arguments );
}

function apply_filters_ref_array( $name, $args ) {
	$default = array_shift($args);
	return event_registry()->apply( $name, $default, $args );
}

function remove_filter( $name, $listener, $priority = 10 ) {
	return event_registry()->silence( $name, $listener, $priority );
}

function remove_all_filters( $name, $priority = false ) {
	return event_registry()->silenceAll( $name, $priority );
}

function current_filter() {
	return event_registry()->firing();
}

function current_action() {
	return event_registry()->firing();
}

function doing_filter( $filter = null ) {
	return event_registry()->listened( $filter );
}

function doing_action( $action = null ) {
	return event_registry()->listened( $action );
}

function add_action( $name, $function_to_add, $priority = 10, $accepted_args = 1 ) {
	return event_registry()->listen( $name, $function_to_add, $priority, $accepted_args );
}

function do_action($name, $arg = '') {
	$args = array();

	if ( is_array($arg) && 1 == count($arg) && isset($arg[0]) && is_object($arg[0]) ) { // array(&$this)
		$args[] =& $arg[0];
	} else {
		$args[] = $arg;
	}

	if ( func_num_args() > 2 ) {
		$args = array_merge($args, array_slice(func_get_args(), 2));
	}

	event_registry()->call($name, $args);
}

function did_filter( $name ) {
	return event_registry()->fired( $name );
}

function did_action( $name ) {
	return event_registry()->fired( $name );
}

function do_action_ref_array( $name, $arguments ) {
	event_registry()->call( $name, $arguments );
}

function has_action($name, $listener = null) {
	return event_registry()->hasListener( $name, $listener );
}

function remove_action( $name, $listener, $priority = 10 ) {
	return event_registry()->silence( $name, $listener, $priority );
}

function remove_all_actions( $name, $priority = false ) {
	return event_registry()->silenceAll( $name, $priority );
}