Recursion Bug?

Hi guys,

I've got an object I'm writing to parse a series of really basic SQL
strings and output the data as a heirarchical DOM Object. Now, I'm
having a problem with recursion. The recurseQueries Method is being
called once, and then segfaulting apache when it calls itself. My code's
not going into an infinite recursion, but a backtrace of the httpd
process indicates that's what's happening. I don't know, maybe I've
missed something outstandingly obvious, but I can't see where it's going
wrong.

The code is located at http://azmoo.net/work/SQLParser.inc.phps and the
backtrace is at http://azmoo.net/work/sql_backtrace.txt

Any help would be greatly appreciated.

Cheers,
Matt