swa66 - 8:11 pm on Feb 7, 2013 (gmt 0)
If a hello world in php is working in a html file: then you're set: php works.
Apparently you're trying to get something pre-made already written in php to work. What exactly ?
Googling for C5T_ROOT and comment.php I find references to something called "Gentlesource comment script". It that what you're trying to use ?
As far as comment fields go: do know that unless you incorporate countermeasures such as a strong CAPTCHA, banning of known bad sources, and a lot of moderation, this is a huge can of worms.