PHP and concurrent file access

Question

I\'m building a small web app in PHP that stores some information in a plain text file. However, this text file is used/modified by all users of my app at some given point i

Answer 1

You should put a lock on the file

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

if (flock($fp, LOCK_EX)) {  // acquire an exclusive lock
    ftruncate($fp, 0);      // truncate file
    fwrite($fp, "Write something here\n");
    fflush($fp);            // flush output before releasing the lock
    flock($fp, LOCK_UN);    // release the lock
} else {
    echo "Couldn't get the lock!";
}

fclose($fp);

Take a look at the http://www.php.net/flock