Good and Bad PHP Code

When interviewing a PHP developer candidate for a job at SitePoint, there is one question that I almost always ask, because their answer tells me so much about the kind of programmer they are. Here’s the question: “In your mind, what are the differences between good PHP code and bad PHP code?”

The reason I like this question is because it tests more than just a candidate’s encyclopedic knowledge of PHP’s functions. Zend’s PHP certification does a good job of that (as does the test that Yahoo! issues to applicants for its PHP developer jobs, apparently).

Rather, the answer to this question tells me whether a PHP developer has, for example, experienced the pain of working with poorly-written code inherited from a careless predecessor, and whether he or she will go the extra mile to save the rest of the team from that same pain.

I don’t have a set notion of the perfect answer to the question, but I do know the kinds of things I’m hoping to hear. Just off the top of my head:
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