When we process a file in PHP, we may often need to acquire a lock so that other scripts cannot edit the same file at the same time. There is a flock() function in PHP which can help us lock the file we want to process. But there is one issue we should take care.Recently, ffb encountered one issue while he was trying to lock a file handle. The codes are below:$filename = "/tmp/lock.txt";    $fp = fopen($filename, "r+");  if (!$fp) {      die("open failed.");  }    i...