SplFileObject::flock

(PHP 5 >= 5.1.0, PHP 7)

Portable file locking

public bool SplFileObject::flock ( int $operation [, int &$wouldblock ] )

Locks or unlocks the file in the same portable way as flock().

Parameters:

operation

operation is one of the following:

LOCK_SH to acquire a shared lock (reader).
LOCK_EX to acquire an exclusive lock (writer).
LOCK_UN to release a lock (shared or exclusive).
LOCK_NB to not block while locking (not supported on Windows).

wouldblock

Set to TRUE if the lock would block (EWOULDBLOCK errno condition).

Returns:

Returns TRUE on success or FALSE on failure.

Examples:

SplFileObject::flock() example

<?php
$file = new SplFileObject("/tmp/lock.txt", "w");
if ($file->flock(LOCK_EX)) { // do an exclusive lock
    $file->ftruncate(0);     // truncate file
    $file->fwrite("Write something here\n");
    $file->flock(LOCK_UN);   // release the lock    
} else {
    echo "Couldn't get the lock!";
}
?>