On the Exakat GitHub account Damien Seguy has put together a pretty complete list of static analyzers you can use for your PHP applications.

The list is broken down into the types of scanners:

• Bugs finders
• Coding standards
• DIY
• Fixers
• Metrics
• SaaS
• Misc

Each section includes a good list of tools and links to each of them (usually just to other GitHub repositories but some go to actual project pages). There's a lot of them to look through but be careful to evaluate the current state of the project. Just because it's linked here doesn't mean it's a complete tool.