Has anyone ever done anything with Magic Parser and modx.
Im trying to use this within a snippet and return the output into a Chunk.
I'm not familiar with Modx i'm afraid but if it has the capability (or maybe a plugin) that enables you to execute arbitrary PHP code within a snippet / chunk then it would be no problem to include MagicParser.php (make sure to use require_once() rather than require() if there are likely to be multiple instances on a page) and output accordingly.
As an example, if one were working in WordPress, the Exec-PHP plugin can be used to execute arbitrary PHP code within a post, so Modx may have something very similar, if not supported natively.
Hope this helps!