The writable file /proc/[pid]/oom_adj controls a processes likelihood (oom_score) of being selected by oom-killer if invoked. Increasing php's adj value would be the easiest way. You can check any processes score with # cat /proc/[pid]/oom_score.
OOM杀手 - 只杀死PHP实例
I have a cPanel server with several WordPress sites. Sometimes (once a month), a big PHP loops occurs and OOM Killer starts (>8 Gb RAM usage). It kills all PHP instances, this fix the problem (out of memory and CPU usage), but kills other services too, like DNS (named), mail server (exim), webmail (cpanel), and so.
How can I configure OOM Killer to kill only PHP instances?