[php] Is there a code obfuscator for PHP?

You can try PHP protect which is a free PHP obfuscator to obfuscate your PHP code.
It is very nice, easy to use and also free.
EDIT: This service is not live anymore.

As for what others have written here about not using obfuscation because it can be broken etc:
I have only one thing to answer them - don't lock your house door because anyone can pick your lock.
This is exactly the case, obfuscation is not meant to prevent 100% code theft. It only needs to make it a time-consuming task so it will be cheaper to pay the original coder. Hope this helps.