Magento How to debug blank white screen

Question

I have an error in my Magento backend that results in a blank screen (WSOD). I have set errors to on in admin but there is nothing being created in var/logs/. (I have checke

Answer 1

Whenever this happens the first thing I check is the PHP memory limit.

Magento overrides the normal error handler with it's own, but when the error is "Out of memory" that custom handler cannot run, so nothing is seen.