I am currently debugging a script that constantly runs into OutOfMemory exceptions. It is run as a cronjob and usually runs fine, but when the cronjob wasn’t run for a while (for whatever reason) the script has to handle to many elements that queued up and will run into a OutOfMemory exception.
From examining the code I was not able to spot the problem. I believe one of the iterative function calls might leak memory, but I am not sure which one and where. Is there an option to get PHP to dump the heap, when an OutOfMemory exception occurs? I might be able to spot the problem from there (most likely).
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Answer
While I was not able to find a “dump heap on Exception” option, I did find get_defined_vars() which is basically a heap dump if called from a global scope. Using this I was able to see that there where hundreds (actually thousands) of still referenced database rows hanging around in my memory. This was due to a not freed mysql result resource somewhere in the infamous function that caused the leak. I found it and fixed it. It runs well now.