hi all, What is the best, optimized and free way to protect my source code (i mean encrypt in a way hard to decrypt for humans)?

actually I want to protect my website and CMS, as php files are just simple text files. anyone who knows a little bit of php can modify in an illegal way.

I have also learned about Zend Guard, IonCube etc... I dont want a paid solution, or a ready made solution. any idea ?