You can try one of the many free php obfuscation services online (just google it) - they should work and give a basic level of protection.

What I've done in the past is write separate the project. Certain expects of the project I would store on a different server that only I had access to. Then the main project would make http requests to the offsite scripts to get data. This way you get the data you need but the people have no idea how you're doing it.

If you are willing to pay for it, there are many solutions, e.g. zend guard or ioncube. There are free too, but i haven't seen a good one yet.

You can use php encryptor or zend encryptor in order to protect your few pages. Your code cannot be changed after encryption but function properly without any problem.

You can encode part of the php code and decode the code on execution with certain conditions

Thanks for sharing these tips here, even though it's an old thread. I too have problems with it for awhile now.

PHP code is not obvious to the closure client. It can just saw provided that you have authoritative rights to the server however any other way, you can not. The excuse for why
behind that is since php is a server side scripting dialect.

As mentioned above there are lots you can choose:

NEW PHP Encoder 8 - PHP Encoder, protection, installer and performance tools from ionCube
PHP Encode Your Application to Protect Your Code with Zend Guard - Zend.com

There are free ones online as well, just google it ("encrypt php code").

http://en.wikipedia.org/wiki/Obfuscation_(software)