I have some PHP source code that I\'m hosting with hosting company XYZ. I\'m using a PHP encryption software like Zend Guard or ionCube to protect the source from being view
Why exactly do you need to encrypt your source code? If you are sporting this as a safe-guard against potential hackers, then please believe when I say that if they really wanted to decrypt your source code, they would do it. It is possible with ionCube, last time I checked.
As far as performance impacts, I believe Zend is a tad bit faster than ionCube due to it not requiring any extra files. But like I said before, don't rely on encryption for anything.