I used to do a lot of hiring for LAMP resources and found that often, someones framilarity with any language had little relationship to their ability to troubleshoot and debug code. If you are looking for project work with clearly defined objectives and deliverables (what IT project is EVER clearly defined) then LAMP proficiency is good enough).
Peronsally, like to give them a busted website running on an issolated VM and two hours to fix it. They can have google, and whatever reference material they need and ask any questions they want. To torture them, do everything from messed up permissions on directories, bad apache configs, bad code, dynamic code, wonky databases, and bad SQL Queries. See how far they get but also how they troubleshoot. What do they prioritize first? Do they write quick scripts from the command line to test database connectivity?
The goal is not to get the website functioning but to see what they fix, how they fix it, and what priority they placed which pieces.