Non tech founder looking to create a straight forward code test.

I need to hire programmers for my startup and I'm not sure how to tell if the people I interview are any good at it. I would like to create a 20 question test with 5 questions in each of these languages. PHP, JAVASCRIPT, AJAX, and MYSQL. Can you help by giving me a question and correct answer for any one of these languages? I will use your questions to compile the test, difficult but not impossible would be great. Thanks in advance to those that participate!!!