<?php
function getlock($filename, $lockwait = -1 /* seconds */)
{
	$lock = new stdClass;
	$lock->filename = $filename;
	$lock->fp = fopen($filename, "w");

	if (!$lock->fp)
		return NULL;

	$lstat = fstat($lock->fp);
	if (!$lstat) {
		fclose($lock->fp);
		return NULL;
	}

	pcntl_signal(SIGALRM, function() {}, false);

	pcntl_alarm(1);
	while (!flock($lock->fp, LOCK_EX)) {
		pcntl_alarm(0);
		clearstatcache(true, $filename);
		$nstat = @stat($filename);
		if (!$nstat || $nstat['ino'] != $lstat['ino']) {
			fclose($lock->fp);
			$lock->fp = fopen($filename, "w");
			if (!$lock->fp)
				return NULL;

			$lstat = fstat($lock->fp);
			if (!$lstat) {
				fclose($lock->fp);
				return NULL;
			}
		}

		if (--$lockwait < 0) {
			fclose($lock->fp);
			return NULL;
		}

		pcntl_alarm(1);
	}
	pcntl_alarm(0);

	clearstatcache(true, $filename);
	$nstat = @stat($filename);
	if (!$nstat || $nstat['ino'] != $lstat['ino']) {
		fclose($lock->fp);
		return getlock($filename, $lockwait);
	}

	return $lock;
}

function releaselock($lock)
{
	unlink($lock->filename);
	fclose($lock->fp);
}
?>