We're trying to setup monitoring (zabbix), for webapps that return white page of death. Apps are PHP based.

From what I know, white screen of death can be caused by number of issues, memory issues, syntax errors etc. 

So I want to ask, is it better to rely on webserver returning 50x code, or there can be (somehow) posibility to get return code 200, but rendering page is empty(white) ?