If you've been using the PHP Mess Detector (PHPMD) to help clean up problem areas in your applications, but have needed more than just the basic rules that it comes with, you're in luck. Manuel Pichler has put together a new post for his blog about creating custom rules sets for the tool.
PHPMD can be seen as an one level down/low level equivalent to PHP_CodeSniffer. It is a simple command line tool that can be used to check your application's source code for possible bugs, suboptimal or overcomplicated code. The current release of PHPMD ships with three default rule sets.
The first deals with code size, the second checks for unused variables and the like and the third looks at naming conventions. He shows how to take one of the structures from one of these three and create a new rule. For his example it's a measurement of cyclomatic complexity. He also shows you how to exclude certain rules that might come in another set so you don't have to completely redefine to use pre-existing rules.