memory leak - how to find it?

I am trying to debug a php script that I downloaded, which has a memory leak in it. I was looking for a way to find what variables were in php's memory, and what size, they were, but I couldn't find anything? The script is a off-line wiki conversion tool (walks through a wiki to create a bunch of html files for off line viewing). As the tools walks the files, and does the conversion, I can see the memory consumption go up and up as it walks the files, until it hits the mem limit, and crashes. Any suggestions appreciated. Thanks -Robin