PHP/HTML in pages plugin

I'm having difficulty with the pages manager plugin.  When I am creating a page, and switch to 'source code' view, I can enter the source code I would like.  However, after I have saved the page and go back, it has all been erased.  I'd like to insert some php code, or even some static html, but it keeps wiping everything out except for the text.  I've even gone so far as enter the html in the field directly in phpmyadmin, however it still doesn't work.

 

It would seem the 'correct' way to do what I would like to do is to create a new plugin, however I don't believe what I'm trying to do warrants the complication.

 

Any help getting more than text/ images/ links to come up from the pages plugin would be helpful.  Thank you!