PHP Unique process

UniqueProcess.php

<?php

/**
 * This class allows us to run only one instance of the process
 *
 * Example:
 *
 *   $uniqueProcess = new UniqueProcess('/var/tmp/some_process_name.lock');
 *   if (!$uniqueProcess->begin()) {
 *       die();
 *   }
 *
 *   someLongProcess();
 *
 *   $uniqueProcess->finish();
 *
 * Class UniqueProcess
 */
class UniqueProcess
{
    /**
     * Pointer to lock file
     * @var resource
     */
    protected $lockFilePointer;

    /**
     * Path to lock file
     * @var string
     */
    protected $fileLockPath;
  
    public function __construct($fileLockPath)
    {
        $this->fileLockPath = $fileLockPath;
    }

    /**
     * Method returns true if file was locked, false otherwise
     * @return bool
     */
    public function begin()
    {
        if (!$this->lockFile()) {
            return false;
        }
        return true;
    }

    /**
     * Method releases lock
     */
    public function finish()
    {
        $this->releaseLock();
    }

    /**
     * Method returns true if file was locked
     * @return bool
     * @throws Exception
     */
    protected function lockFile()
    {
        $this->lockFilePointer = fopen($this->fileLockPath, 'w');

        if ($this->lockFilePointer === false) {
            throw new Exception('Unable to create/open lock file');
        }

        return flock($this->lockFilePointer, LOCK_EX | LOCK_NB);
    }
  
    /**
     * Release file lock even in case of Fatal error
     */
    public function __destruct()
    {
        $this->releaseLock();
    }

    /**
     * Method releases lock
     */
    protected function releaseLock()
    {
        if (is_resource($this->lockFilePointer)) {
            fclose($this->lockFilePointer);
        }
    }
}