You guys may also want to check out newdreamers addition to this PHP block tutorial. The tutorial shows you how to add it directly from your builder page. This avoid the phpmyadmin approach.

Here's the link:
http://www.boonex.com/unity/blog/entry/How_to_enable_PHP_block_in_the_Page_Builder

Hopefully it didn't get cut off, but if it did here's a tinyurl version of it:

http://tinyurl.com/newdreamer

...sip...