PHP max_execution_timeout is not evaluated

I am running PHP 7.0.22 and have a problem while trying to set the max_execution_timeout option inside a PHP script. max_execution_timeout is set correctly but it is not taken into consideration by PHP:

<?php

...
$iniset = ini_set('max_execution_time', 120 * 60); // 2 hours
$iniget = ini_get('max_execution_time'); 
var_dump($iniset, $iniget);
...

And here is the output:

string '30' (length=2) string '7200' (length=4)

( ! ) Fatal error: Maximum execution time of 120 seconds exceeded in file.php on line 425

As you can see, the limit is increased to 7200 seconds, but then the script execution breaks after 120 seconds, as shown by the fatal error.

How is that possible?

P.S.: I have Xdebug installed, maybe it can cause this issue.

Thank you for your attention.