Could someone give a bit of a pointer here...

I'm not sure if this is the correct list to post this, but I was wondering if someone could lend a hand and point me in the right direction here? For interest sake, last week, I successfully wrote/compiled/ran an extension module (a basic arc4 cipher implementation...yes I know there is already one but like I said it was in interest...) Curiosity unsatisfied, I've gone on to further poking round in the php source tree... Today I thought I'd check out how include() is implemented...but I cant seem to figure this one out... I've gone up and down the tree, and found the most promising stuff in the following files: zend_compile.c (line 1965) zend_do_include_or_eval(); zend_execute.c (line 1975) (switch statement) case ZEND_INCLUDE_OR_EVAL and several interesting entries in other files, but still nothing really concrete I probed a bit deeper and ended up looking at things like "HashTable *function_tables" and decided I didnt really know where I was going here... I figured I would save a bit of time and 'brain strain' and talk to someone who knows this stuff... First, where is include() declared (so I can at least find the starting point :), and is it somehow built into the run-time compiler so that it's not quite as straightforward as I thought... Is anyone able to explain the principles behind all this, or at least point me in the right direction to start figuring this out? Cheers, Andrew McBeath