It seems IPS does not want anything to do with any sort of PHP.
Here's the post in question: http://www.gamedev.net/topic/667797-confused-can-i-use-php-to-make-a-game/?view=findpost&p=5225258
Here's the code I tried to include: http://pastebin.com/X5WdZSGM
And here is a sample below:
<?php
header('Content-Type: text/plain');
print file_get_contents('php:'.'//input');
I'll try some things to coerce dumb forum software to post PHP.EDIT#9001:
Well, I've solved the mystery. IPS will banjo parts of your post if you make any mention of (standard PHP process handles). More specifically, IPS will censor any part of your post that contains this exact string, sans invisible whitespace: php:?//
EDIT#9002:
Holy hell, it censors it outside of the code block as well! What is this madness!?