If you’re serious about protecting your code from prying eyes then I would stay well away from any PHP based encoding system.
The Source Guardian website came to my rescue here:
[font=verdana]Any PHP encryption program needs to decrypt the file at some time, so the code will be theoretically available to experienced crackers during its execution.
I can’t say don’t use Source Guardian because I’ve never used it myself, but their website hasn’t convinced me.
[/font] The ionCube loaders work best if they can be installed on the server, but if you don't have access to this they are loaded at run-time instead (so installation isn't strictly necessary). All you need to do is make sure the files are on the server in the right place!
IMO, CodeLock is only going to discourage casual observers and I wouldn’t use it (a personal choice). Encoded source can be decoded in seconds. A related thread can be found here: Free PHP Script Encoder