This is from the CMS guys:
Just to explain my problem better, it doesn't work putting the in-script in my CMS templates, so I had it in my index.php directly before. This caused my CMS not to be able to produce valid 404 pages (404 headers) so I searched for another solution for the IN code.We use the PHP function eval(); in ExpressionEngine to evaluate PHP in templates. I am testing in PHP 5.1.2 and using virtual causes a complete ceasing of parsing in ExpressionEngine. It is very possible that the PHP developers will not allow its usage in eval() without special coding.