改进防止 php 脚本运行两次（使用 cronjobs）

Question

I'm like to improve script below, or maybe know if exist a better way to rewrite to better results.

I use this on two files cron1.php and cron2.php executed every 5 seconds and need to prevent running twice.

Script execution time depends of filesize, most of the time took around 2 seconds, but for huge files can take 25/30 seconds, for this i need to stop execution.

I'm on right way? Any suggestion to improve?

$fp = fopen("cron.lock", "a+");
if (flock($fp, LOCK_EX | LOCK_NB))
{
  echo "task started\n";
  // Here is my long script
  // Cron run every 5 seconds
  sleep(2);

  flock($fp, LOCK_UN);
}
else
{
    echo "task already running\n";
    exit;
}
fclose($fp);

Answer 1

I generally do a file operation like dumping the getmypid in the lock file. So externally I can know which pid has locked it. In some debugging cases, that is helpful. Finally, unlink the lock file when you are done.