Locker.php

<?php

namespace AppBundle\Service;


class Locker
{
    protected $baseDir;

    public function __construct($dir)
    {
        $this->baseDir = $dir;
    }

    public function acquireLock($file)
    {
        $filename = $this->baseDir . DIRECTORY_SEPARATOR . $file;
        if (!$this->isLocked($file)) {
            file_put_contents($filename, ((new \DateTime('now'))->format(\DateTime::ATOM)));
            chmod($filename, 0777); // if the file cant be opened for writing later, getting the lock will fail
        }
    }

    public function releaseLock($file)
    {
        $filename = $this->baseDir . DIRECTORY_SEPARATOR . $file;
        if ($this->isLocked($file)) {
            unlink($filename);
        }
    }

    public function isLocked($file)
    {
        return file_exists($this->baseDir . DIRECTORY_SEPARATOR . $file);
    }
}