From phpBB Development Wiki
The coding guidelines for phpBB4 are based on the coding guidelines document for phpBB3. Information on templating, styling, translating, the file structure and the DBAL has been removed. A few changes were made. The most significant ones being:
- Spaces instead of tabs
- CamelCase for all identifiers
- No closing PHP tag
- New file header
- Additional guidelines on object oriented concepts (Interfaces, Classes, etc.)
It's likely that this document will need to be extended once more details of phpBB4 become clear. For now it should sufficiently regulate the use of PHP to start development.
The current document can be found on github in naderman's coding-guidelines branch: http://github.com/naderman/phpbb/blob/coding-guidelines/docs/coding-guidelines.markdown A small tool for converting the document to HTML can be found in the develop/ directory.