Running a PHP script every 5 minutes and avoiding race conditions

Question

I have a php script that needs to run once every 5 minutes. Currently I\'m using a cron job to run it (and it works great) but my host only allows a minimum time of 15 minut

Answer 1

If you cannot do what @Brandon suggested, I would recommend the approaching this in the same way I did when writing a daemon in PHP (not the best solution but I was practically forced to do this).

In my case as well the script accessed a (log)file and did processing on it, afterwards inserting the results in the database. So to ensure that I don't have two files running at the same time, I created a "status" file on which the script acquired a lock and if not able to do so if failed gracefully.

$fh = fopen('status_file', 'w');

/**
 * LOCK_NB is required because otherwise your script would stall until
 * a lock is aquired, queing a bunch of scripts.
 */
if(!flock($fh, LOCK_EX | LOCK_NB)) {
  exit 1; // our job is done here
}