Session concurrency

session.php

<?php

// Native handlers

//ini_set('session.save_path', 'tcp://127.0.0.1:11211');
//ini_set('session.save_handler', 'memcache');

//ini_set('session.save_path', '127.0.0.1:11211');
//ini_set('session.save_handler', 'memcached');

// Custom handler

class FileSessionHandler
{
    private $savePath;

    function open($savePath, $sessionName)
    {
        $this->savePath = __DIR__.'/session';
        if (!is_dir($this->savePath)) {
            mkdir($this->savePath, 0777);
        }        
        return true;
    }

    function close()
    {
        return true;
    }

    function read($id)
    {
        return (string)@file_get_contents("$this->savePath/sess_$id");
    }

    function write($id, $data)
    {
        var_dump('write() start '.date('His'));
        sleep(2);
        $ret = file_put_contents("$this->savePath/sess_$id", $data) === false ? false : true;
        sleep(2);
        var_dump('write() end '.date('His'));
        return $ret;
    }

    function destroy($id)
    {
        $file = "$this->savePath/sess_$id";
        if (file_exists($file)) {
            unlink($file);
        }

        return true;
    }

    function gc($maxlifetime)
    {
        foreach (glob("$this->savePath/sess_*") as $file) {
            if (filemtime($file) + $maxlifetime < time() && file_exists($file)) {
                unlink($file);
            }
        }

        return true;
    }
}

$handler = new FileSessionHandler();
session_set_save_handler(
    array($handler, 'open'),
    array($handler, 'close'),
    array($handler, 'read'),
    array($handler, 'write'),
    array($handler, 'destroy'),
    array($handler, 'gc')
    );

register_shutdown_function('session_write_close');

$start = session_start();
var_dump('started '.date('His'));

var_dump(array(
  'start'   => $start,
  'session' => $_SESSION,
));

$key = isset($_GET['key']) ? $_GET['key'] : 'key';
$data = isset($_GET['data']) ? $_GET['data'] : 'data';

var_dump('set '.date('His'));
$_SESSION[$key] = $data;

var_dump('sleep '.date('His'));
sleep(5);
var_dump('sleep end '.date('His'));

var_dump($_SESSION);

var_dump('end of script '.date('His'));