Which language would annoy a PHP user?

We have nobody who coordinates the programmers at the company. Everybody uses the technology he wants.

Which programming language would you suggest to learn that would annoy a PHP user (who knows a bit of Java) and give him a bad time if he has to take over a project?

>>11
Only if you have concurrent access to them.

But no, seriously, there's nothing more I hate than doing a fucking autopsy to some hack's code to see where the values for their handy global variables come from.

Rails is the worst exponent in this.