PHP4Mono is a compiler that enables Mono to run PHP code. It translates PHP scripts to Common Intermediate Language (CIL). Like that PHP scripts can be executed as console applications on Mono. You can even build GUIs directly from within a PHPscript!
PHPCoder is a web based front end to the excellent Turck MMCache and eAccelerator encoding/cache engines. PHPCoder makes it easy to distribute compiled PHP scripts rather than source code and has built in options to allow you to restrict a script.