The Codacy.com blog has posted a review of various static analysis tools for PHP-based applications. These tools can help provided quality and consistency in your code in a more automated way.
Maintaining code quality over time is a hard challenge. It becomes even harder in large projects developed by many programmers. Each person has different code styles and different ways to approach problems. Over time, this may result in confusing and unmaintainable code. Static analysis tools can help developers solve this problem, they enforce coding standards, detect common errors and cleanup code blocks.
Tools mentioned in the post include: PHP_CodeSniffer, the PHP Mess Detector and the PHP Copy & Paste Detector. Each comes with an example of the command to execute it and some sample results. They also talk briefly about where and how these tools could fit into your current workflow, either during development or as a part of a full deployment process.