How to use "poor man's cron" with PHP?

Question

I'm trying to implement a "poor man's cron" to run my PHP script only every 10 minutes (if no one visits the page it doesn't run until someone does)

Here is what I have:

$current_time = time();

if($current_time >= $last_run + (60 * 10)) {
    echo 'foo';
    $last_run = time();
} else {
    echo 'bar';
}

What I'm expecting to get is "foo" on the screen once and when I refresh the page I want to see "bar". If I refresh the page after 10 minutes it should be "foo" again for once and then "bar" until another 10 minutes has passed.

Currently it prints out "foo" all the time.

HTTP request timeout is around 30 seconds. If you want to refresh the page periodically, do it on client side (via javascript, or <meta http-equiv="refresh" content="600"> — Ruslan Osmanov
– Ruslan Osmanov, Commented Nov 25, 2016 at 17:18

Devon Bessemer · Accepted Answer · 2016-11-25 17:18:27Z

3

Variables don't hold their value after execution finishes. All memory is cleared when the PHP script finishes, meaning the next time the script is run, PHP will not know what $last_run was. You need to store $last_run somehow, possibly using the filesystem or database.

Using the filesystem, you could do:

$last_run = file_get_contents('lastrun.txt');
if (!$last_run || $current_time >= $last_run + (60 * 10)) {
   echo 'foo';
   file_put_contents('lastrun.txt', time());
} else {
    echo 'bar';
}

answered Nov 25, 2016 at 17:18

Devon Bessemer

35.6k10 gold badges77 silver badges102 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

user1589375 Over a year ago

This did the trick! I must have mixed some other language there when I tried to store the value straight into the variable. Haven't used PHP in a long time. Need to wait 5 mins until I can accept this as an answer. Thank you!

OptimusCrime · Accepted Answer · 2016-11-25 17:21:20Z

2

This is unfortunately not how PHP works. PHP starts a new process when you access the web server, and dies afterwards. You would need a script that runs forever, using something like:

while (true) {
    // Check if we should do anything, or just keep spinning
}

However, PHP was not designed for these kinds of tasks, and this script will most likely die sooner or later for either max execution time, memory limits or something else.

A functional "poor mans cronjob" would instead require you to check the current timestamp and do whatever should be done since the last visit before you continue. This would "fake" the illusion of having a cron job running.

edited Nov 25, 2016 at 17:21

answered Nov 25, 2016 at 17:19

OptimusCrime

14.9k13 gold badges63 silver badges98 bronze badges

2 Comments

Aniket Sahrawat Over a year ago

Are you sure that while(true) won't overload the server and return a 500 error code?

OptimusCrime Over a year ago

@AniketSahrawat You'd most likely need some sort of sleep or something in this loop. It was meant as a "this is how you would have to do it, but it won't work". Constructing a while (true) given the right php settings would work, but the script would die after a while.

Collectives™ on Stack Overflow

How to use "poor man's cron" with PHP?

2 Answers 2

1 Comment

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related