Internal Server Error after long time running of php script

Question

I have some db query in my php file, approximately after 40 second, happened INTERNAL SERVER ERROR, though in php.ini file this settings are set:

memory_limit         8192M
max_execution_time   120

I think this settingst is enough, other what reason may causes INTERNAL SERVER ERROR after long time running of php script?

Answer 1

set

ini_set('max_execution_time' ,0);       
ini_set('set_memory_limit', -1)