<?php
error_reporting(E_ALL);

function cleanup($filename){
	unlink($filename);
}

$filename = tempnam(getcwd(), 'tmp');

register_shutdown_function('cleanup', $filename);

set_time_limit(3);
sleep(4);
?>

<?php
error_reporting(E_ALL);

ignore_user_abort(false);

function cleanup($filename){
	unlink($filename);
}

$filename = tempnam(getcwd(), 'tmp');

register_shutdown_function('cleanup', $filename);

set_time_limit(20);
sleep(30);
?>

<?php
error_reporting(E_ALL);

ignore_user_abort(false);

function cleanup($filename){
	switch(connection_status()){
		case 1:
		case 2:
		case 3:
		unlink($filename);
		break;
	}
}

$filename = tempnam(getcwd(), 'tmp');

register_shutdown_function('cleanup', $filename);

set_time_limit(5);
do{
	echo 'foo';
}while(true);
?>

<?php
// Running on a Windows XP machine with an Apache server
error_reporting(E_ALL);

ignore_user_abort(false); // Does indeed affect behavior now

function cleanup($filename){
	switch(connection_status()){
		case 1:
		unlink($filename);
		case 2:
		case 3:
		break;
	}
}

$filename = tempnam(getcwd(), 'tmp');

register_shutdown_function('cleanup', $filename);

set_time_limit(5);
// Purposely causes a CONNECTION_TIMEOUT
do{
	echo 'foo';
}while(true);
?>

<?php
error_reporting(E_ALL);
ignore_user_abort(false); // Need to ensure behavior is false so in case of abort the mutex will be removed

/* Reference Material
 *
 * http://en.wikipedia.org/wiki/ACID
 *
 */
 
/*************/
/* Test Code */
/*************/
$mutex = new Mutex(getcwd() . '\tmp000.tmp', 10, 0755, true);
$mutex->acquireLock();

// Purposely causes a CONNECTION_TIMEOUT
do{
	echo 'foo';
}while(true);
/*************/

class Mutex {
	/* Private variables */
	
	var $filename;			// The file to be locked
	var $timeout = 60;		// The timeout value of the lock
	var $permission = 0755;	// The permission value of the locked file
	
	/* Constructor */
	
	function Mutex($filename, $timeout = 1, $permission = null, $override = false){
		// Append '.lck' extension to filename for the locking mechanism
		$this->filename = $filename . '.lck';
		// Timeout should be some factor greater than the maximum script execution time
		$cfgtime = @get_cfg_var('max_execution_time');
		if($override === true){
			if($timeout >= 1) $this->timeout = 2* $timeout;
			set_time_limit($this->timeout / 2);
		}elseif($cfgtime !== false){
			if($timeout >= 1) $this->timeout = $timeout * (2 * $cfgtime);
		}
		// Should some other permission value be necessary
		if(isset($permission)) $this->permission = $permission;
		register_shutdown_function(array($this, "lockAbort"));
	}
	
	/* Methods */
	
	function acquireLock(){
		// Create the locked file, the 'x' parameter is used to detect a preexisting lock
		$fp = @fopen($this->filename, 'x');
		// If an error occurs fail lock
		if($fp === false) return false;
		// If the permission set is unsuccessful fail lock
		if(!@chmod($this->filename, $this->permission)) return false;
		// If unable to write the timeout value fail lock
		if(false === @fwrite($fp, time() + intval($this->timeout))) return false;
		// If lock is successfully closed validate lock
		return fclose($fp);
	}
	
	function releaseLock(){
		// Delete the file with the extension '.lck'
		return @unlink($this->filename);
	}
	
	function lockTime(){
		// Retrieve the contents of the lock file
		$timeout = @file_get_contents($this->filename);
		// If no contents retrieved return error
		if($timeout === false) return false;
		// Return the timeout value
		return intval($timeout);
	}
	
	function lockFile(){
		return $this->filename;
	}
	
	function lockAbort(){
		switch(connection_status()){
			case 0:
			break;
			default:
			@unlink($this->filename);
			break;
		}
	}
}
?>