function_override.php

<?php






action_hook('before_user_login', 'my_user_login');
function my_user_login($params)
{
     
     if($params == 'my_login'){
	 return function ()  { return print 'my_login <br>'; };
	 }

 }



function user_login($params)
{
    $override = exec_action('before_user_login', $params);
    if (is_array($override)) {
        foreach ($override as $resp) {
            if(is_object($resp)){
            	 
            	return call_user_func($resp,$params); 
            }
        }
    }
		return 'default login <br>';
 }


print user_login('my_login');

print user_login('something');




// action hook


function exec_action($api_function, $data = false)
{
    global $action_hook_index;
    $hooks = $action_hook_index;

    $return = array();
    if (isset($hooks[$api_function]) and is_array($hooks[$api_function]) and !empty($hooks[$api_function])) {

        foreach ($hooks[$api_function] as $hook_key => $hook_value) {

            if (function_exists($hook_value)) {
                if ($data != false) {
                    $return[$hook_value] = $hook_value($data);
                } else {

                    $return[$hook_value] = $hook_value();
                }
                unset($hooks[$api_function][$hook_key]);

            } else {


                try {
                    if ($data != false) {
                        $return[$hook_value] = call_user_func($hook_value,$data); // As of PHP 5.3.0
                    } else {
                        $return[$hook_value] = call_user_func($hook_value,false);
                    }
                } catch (Exception $e) {

                }

            }
        }
        if(!empty($return)){
            return $return;
        }
    }
}

$action_hook_index = array();
function action_hook($function_name, $next_function_name = false)
{
    global $action_hook_index;

    if (is_bool($function_name)) {
        $action_hook_index = ($action_hook_index);
        return $action_hook_index;
    } else {
        if (!isset($action_hook_index[$function_name])) {
            $action_hook_index[$function_name] = array();
        }

        $action_hook_index[$function_name][] = $next_function_name;

        //  $index .= ' ' . $function_name;
    }
}