Run a PHP script every second using CLI

Question

I have a dedicated server running Cent OS with a Parallel PLESK panel. I need to run a PHP script every second to update my database. These is no alternative way time-wise, it needs to be updated every second.

I can find my script using the URL http://www.somesite.com/phpfile.php?key=123.

Can the file be executed locally every second? Like phpfile.php?

Update:

It has been a few months since I added this question. I ended up using the following code:

#!/user/bin/php
<?php
$start = microtime(true);
set_time_limit(60);
for ($i = 0; $i < 59; ++$i) {
    doMyThings();
    time_sleep_until($start + $i + 1);
}
?>

My cronjob is set to every minute. I have been running this for some time now in a test environment, and it has worked great. It is really super fast, and I see no increase in CPU nor Memory usage.

Answer 1

You could actually do it in PHP. Write one program which will run for 59 seconds, doing your checks every second, and then terminates. Combine this with a cron job which runs that process every minute and hey presto.

One approach is this:

set_time_limit(60);
for ($i = 0; $i < 59; ++$i) {
    doMyThings();
    sleep(1);
}

The only thing you'd probably have to watch out for is the running time of your doMyThings() functions. Even if that's a fraction of a second, then over 60 iterations, that could add up to cause some problems. If you're running PHP >= 5.1 (or >= 5.3 on Windows) then you could use time_sleep_until()

$start = microtime(true);
set_time_limit(60);
for ($i = 0; $i < 59; ++$i) {
    doMyThings();
    time_sleep_until($start + $i + 1);
}