[UK Jimbo]

As it's a scripting language PHP is difficult to "encode" or hide the source of. Two solutions that spring to mind are:

- Compiling the code and distrubiting it as byte code of sorts
- Obfuscating it (I'm sure there are products out there, do a search for "php obfuscator" or "php obfuscate")

The first option might be difficult as I suspect you'll need "not-free" software to create the files and it'll rely on the end user having certain modules installed (it's also unlikely to work with the vBulletin plugin system which evals the code).

Just pointers but I hope it's of some use to you