I created a content type called informational, that has only one field in it, the default body textarea, I added into it
<?php echo 'test';?>, and chose the PHP Filter option, in my page--informational.tpl.php all I'm doing is printing that field, and it's printing it as 'plain text' format. I checked in the DB and it's saved as PHP code.
P.S. I'm an administrator of the site, and I have all permissions.