From phpBB Development Wiki
phpBB's coding guidelines are maintained in its source code repository. You can find the latest versions on area51:
- Rules for Olympus (3.0.x) code are described in http://area51.phpbb.com/docs/30x/coding-guidelines.html
- Rules for Ascraeus (3.1.x) code are described in http://area51.phpbb.com/docs/31x/coding-guidelines.html
These documents are automatically updated when changes are made to them.