Klaus Silveira has submitted a project he's come up with to help PHP developers detect problems in their code via a web-based application - PHPHint.org.
PHPHint is a community-driven, quick and easy to use, online tool that analyzes your PHP code and looks for potential errors, lack of best practices and code smell. It also allows you to clean your code automagically.
It was created to spread the work about the PSR standards and the PHP-FIG group, the importance of getting rid of code smell and applying to standards.
Since it is an open source project, you can help contribute if you'd like to see improvements to the service. It's great that it takes the relatively new PSR standards (PSR-1 & PSR-2) into account when analyzing the code too.