PHP: set_time_limit() seems to have no effect whatsoever

Question

I'm trying to use PHP's set_time_limit() in a normal PHP apache script (not CLI) to limit its max running time. It's not doing anything with system calls or anything similar, we're not using safe mode (we're the owners but not the admins of the server). This is PHP 5.2.4 on Linux (Ubuntu).

Simple test case:

ini_set('max_execution_time', 1);
set_time_limit(1);
$i=0;
while ($i++<100000000000) {} // or anything other arbitrary that takes time
die('Done');

Expected result: something relating to the script execution time being exceeded

Actual result: Done is printed.

Am I doing something obvious wrong? _{(By the way, yes, the script really needs to and can run for too long and need to be aborted, it's unfortunately not something that can be avoided. That is not the point here.)}

Answer 1

Quoting from the manual:

Note:

The set_time_limit() function and the configuration directive max_execution_time only affect the execution time of the script itself. Any time spent on activity that happens outside the execution of the script such as system calls using system(), stream operations, database queries, etc. is not included when determining the maximum time that the script has been running. This is not true on Windows where the measured time is real.

sleep() is among those functions that do not affect the running time of the script

see MPHH's comment on the sleep() page of the manual

Note: The set_time_limit() function and the configuration directive max_execution_time only affect the execution time of the script itself. Any time spent on activity that happens outside the execution of the script such as system calls using system(), the sleep() function, database queries, etc. is not included when determining the maximum time that the script has been running.