PHP code encryption

Hi, I am working in a project for a customer of my company, I am using PHP and I want to prevent my customer from touching my code. The problem that I have to install the application in the customer computer. So, I am looking for a way to encrypt my PHP code. I heard that there is a way but I don't have details. How to do this? Is it legal to be used in a commercial purposes? Is it free? Should I install somthing in the customer's pc to decrypt my code? Could I have some not encrypted pages (eg: config.php) ? Thanks, Hamid Hossain _________________________________________________________________ Help STOP SPAM with the new MSN 8 and get 2 months FREE* http://join.msn.com/?page=features/junkmail