There are others like Zend and Source Guardian but this one is at least as good as the other options. They also offer an online service which is pay-as-you-go so you don't have to buy the software up-front. The free options (and some of the commercial ones) are obfusticators and they can be broken quite easily. Ioncube, Zend and Source Guardian all produce 'byte code' which isn't quite compiled but it is an intermediate step beyond the original source code. If you are thinking of selling a PHP product, then you also have to use some sort of license software (Ioncube also has one of those). Otherwise, people can redistribute your 'byte code' version and you won't have any control over them.