What is clean code? At last night's SFDUG I gave a brief introduction to two complexity metrics—cyclomatic complexity and npath complexity—and how we can use these metrics to gain insight into the readability and maintainability of one's code.

PHPMD is a tool that analyzes and warns about overly complex code. The metrics alone are useful, but having a tool to crunch the numbers automatically is extremely handy. In addition to PHPMD, I recommended using a plugin for one's editor and/or IDE, such as Syntastic for Vim.