encrypt php code

In PHP4.3 we have an encrypt tools which can encrypt some PHP code to protect our company privacy.

But in PHP5.0 those tools can not work.

Does anybody have some way to encrypt PHP code for free or some other way to protect the code privacy?

I only know the Zender gurder has the encrypt tech. but it cost 2000$ each year!

ionCube PHP Encoder http://www.ioncube.com/sa_encoder.php should be cheaper

Thank you.

But in our case, the encoder tools should be free or develop by ourself.