On his SourceRally blog, reign as a new post listing out the "Top 10 Mistakes & Problems" that PHP developers make.

Seeing the number of problems and mistakes PHP coders encounter repeatedly I set out to make this list of the 10 most common problems and mistakes done by PHP coders.

Included on the list are some of the usual suspects:

• Not escaping entities
• Not Escaping SQL input
• Requiring and including files using untrusted data
• Syntax errors

But there's also a few that are just good recommendations and aren't really problems (like using a framework or OOP in an application). Check out the full list here.