Interprocess locking in PHP with Unix domain sockets

socket_lock.php

<?php

/**
 * Try to acquire an arbitrarily-named lock by binding a Unix
 * (family AF_UNIX) datagram (type SOCK_DGRAM) socket to an
 * abstract address corresponding to the lock name. On success,
 * the bound socket resource is returned (or null, on
 * failure). You may either call unlock() with that resource to
 * release the lock explicitly, or rely on the operating system
 * to clean up the socket when the process exits.
 * @param string $name name of the lock to acquire
 * @return resource null if the lock failed, or a socket
 *                  resource on success
 */
static function lock($name) {
    $socket = socket_create(AF_UNIX, SOCK_DGRAM, 0);
    try {
        $bound = socket_bind($socket, "\x00$name");
    } catch (ErrorException $e) {
        socket_close($socket);
        return null;
    }
    return $bound ? $socket : null;
}

/**
 * Explicitly release a lock acquired with lock(). This is only
 * necessary if you need the lock released before the process
 * exits. This function is unnecessary, really, but you might
 * not want to require callers to know their lock is a socket.
 * @param resource $socket
 */
static function unlock($socket) {
    socket_close($socket);
}

?>