fetch_template is giving me Call to undefined function

Okay, I'm making a hack and I have some templates that I need to add to the php page, so I'm using the fetch_template function. However when I do this I get this error

Call to undefined function: fetch_template()


I'm using something identical to this

PHP Code:

eval('$main = "' . fetch_template('main') . '";'); 


and yes I have a template that matches the above ^^

Any suggestions?