[Stasik]

$fp = fopen("/tmp/lock.txt", "w+");

if (flock($fp, LOCK_EX)) { // do an exclusive lock
fwrite($fp, "Write something here\n");
flock($fp, LOCK_UN); // release the lock
} else {
echo "Couldn't lock the file !";
}

fclose($fp);


выдрал из мануала