the goals of our weekly code reviews:

1. Find and eliminate code defects
2. Communication – understand what others are working on
3. Responsibility – reduce code hacks, develop and enforce conventions
4. Discussion on methodology
5. Security best practices (XSS, SQL injection, etc.)
6. Conventions/code style (function and variable naming conventions, etc.), e.g.:
1. http://pear.php.net/manual/en/standards.php
2. http://framework.zend.com/manual/en/coding-standard.html
7. SQL best practices- only return the columns of data you need, etc.
8. REGEX best practices
9. OO best practices
10. Javascript best practices

Here is a PHP Code Review Checklist