PHP Mess Detector (PHPMD) is a static analysis tool for PHP that helps detect potential problems in your code. It identifies a wide range of code issues, including:
PHPMD is configurable, allowing you to define custom rules or use predefined rule sets like "unused code" or "naming conventions." It works similarly to PHP_CodeSniffer, but while CodeSniffer focuses more on style and formatting issues, PHPMD is more focused on the logic and structure of the code.
In summary, PHPMD helps ensure code quality and maintainability by pointing out potential "messes" that might otherwise go unnoticed.