This is a useful article that has basically taken the OWASP Top 10 Vulnerabilities and remapped them to PHP with actual examples.
The Open Web Application Security Project released a helpful document that lists what they think are the top ten security vulnerabilities in web applications.
These vulnerabilities can, of course, exist in PHP applications. Here are some tips on how to avoid them. I’ve included related links and references where relevant.
You can download the detailed OWASP Top 10 Vulnerabilities here.
You can find PHP and the OWASP Top Ten Security Vulnerabilities here.