<?php

/**
 * This class porpose is to execute a code once on the next request using the session as a place to register
 * an instance of the class and execute the code when the object is being unserialized
 *
 *  Created by: Amit Dar
 *  Website: http://www.i-Dev.co.il
 */
class NextRequestScheduler implements Serializable
{
    private $executable_function = null;
    private static $session_var_name = 'next_request_scheduler';

    public function __construct($function_name)
    {
        if(!function_exists($function_name))
        {
            throw new BadFunctionCallException("Passed argument is not a valid function name");
        }

        $this->executable_function = $function_name;
        $_SESSION[self::$session_var_name][] = $this;
    }




    /*@see Serializable::serialize() */
    public function serialize()
    {
        return $this->executable_function;
    }

    /* @see Serializable::unserialize()*/
    public function unserialize($serialized)
    {
        call_user_func($serialized);
        $this->executable_function = null;

        /* unfortunatelly it's impossible to clean up the $_SESSION variable
         * from used instances, since $_SESSION array is not yet populated
         * at the moment of the unserialize function's call.
         *
         * Either you clean it up in a later stage or never clean it up.
         * Possibly, clean old instances out when constructing new instances
         */

    }

}



/******************* USAGE ***********************/

$closures_dont_work = function() {  echo 'hola from closure'; };
function say_hi() { echo 'hi'; }
function say_hello() { echo 'hello'; }


session_start();
new NextRequestScheduler('say_hello');
new NextRequestScheduler('say_hi');

//new NextRequestScheduler($closures_dont_work);
/* The only way to use closures here is to fetch their source code
 * store it in the session and execute it on the next request.
 * Fetching closures source code is possible reading the file having the declaration
 *
 * A better way would be to invoke a member of a class (say user->get_new_forum_posts)
 * and that would require reimplementing the "unserialize" function to use call_user_method
 * rather then call_user_func.
 *
 * Adopt it carefully
 */