Script locking mechanism for one-time-running scripts such as cron scripts

Lock.php

<?php

/**
 * Class Lock
 * Script locking mechanism for one-time-running scripts.
 */
class Lock
{
	private $fp;
	function __construct()
	{
		$this->fp=fopen(__FILE__,'r');
		if (!flock($this->fp,LOCK_EX|LOCK_NB))
			die(sprintf('[%s] The script %s has already been running. Terminated!',date('Y-m-d H:i:s'),basename(__FILE__)));
	}
	function __destruct()
	{
		flock($this->fp,LOCK_UN);
		fclose($this->fp);  
	}
}

?>

testScriptLock.php

<?php

/**
 * This script runs one time at a time.
 */
require_once('Lock.php');
$scriptLock=new Lock();

?>