PHP not being eval'd on a node
If you use print render($content); and your code is displayed as it is on an Informational page ("echo 'test';") you should check PHP code configuration page (?q=admin/config/content/formats/php_code).
Here you set the roles who can use this text filter (by default is the 'administrator') and you enable or disable PHP code evaluator. Ensure that 'PHP evaluator' checkbox is on.
I hope this will help you.