Example of locking and unlocking files with PHP, _PHP tutorial

/*************************************************************************
*file lock
*@author Zeal Li
*http://www.zeali.net/
*
*************************************************************************/
/*
*lock_thisfile: Obtain exclusive lock
*@param $tmpFileStr The file name used as the shared lock file (you can give it any name)
*@param $locktype lock type, the default is false (non-blocking, that is, once the lock fails, it will directly return false). If set to true, it will wait for the lock to be successful before returning
*@return If the lock is successful, return the lock instance (this parameter is required when using the unlock_thisfile method), if the lock fails, return false.
*/

function lock_thisfile($tmpFileStr,$locktype=false){

if($locktype == false)

$locktype = LOCK_EX|LOCK_NB;

$can_write = 0;

$lockfp = @fopen($tmpFileStr.".lock","w");

if($lockfp){

$can_write = @flock($lockfp,$locktype);

}

if($can_write){

return $lockfp;

}

else{

if($lockfp){

               @fclose($lockfp);

                 @unlink($tmpFileStr.".lock");

}

return false;

}

}

/**
*unlock_thisfile: Unlock the previously obtained lock instance
*@param $fp The return value of the lock_thisfile method
*@param $tmpFileStr The file name used as the shared lock file (you can give it any name)
*/
function unlock_thisfile($fp,$tmpFileStr){

@flock($fp,LOCK_UN);

@fclose($fp);

@fclose($fp);

@unlink($tmpFileStr.".lock");

}
?>

//Usage examples
$tmpFileStr = "/tmp/mylock.loc";
// Wait for the operation permission to be obtained. If you want to return immediately, set the second parameter to false.
$lockhandle = lock_thisfile($tmpFileStr,true);
if($lockhandle){
// All transactions that require exclusive processing are performed here.
// ... ...
// Transaction completed.
​ unlock_thisfile($lockhandle,$tmpFileStr);
}
?>