Does cPanel kills php processes? I run PHP as cgi but somehow the script will stop in the middle. I have set max_execution_time and max_input_time as 0, no fatal errors in the script. I see nothing in the log too.
If I had to take guess.. i'd say check syslog. Maybe Linux's OOM Manager is killing it because your machine is low on memory? Is the php script memory intensive? There could be a number of reasons why, but i'd start there.
I don't find any problem in the system logs. Memory shouldn't be an issue because the server has 8 GB RAM.
Another thing I found is my logged-in sessions will get automatically logged out in 5 minute interval (i.e. 5, 10, 15, 20th minutes). For this, I checked my cron jobs and found only Cacti's poller and dcpumon is running on this time interval. Which could cause the problem?