WordPress Coding Standards

[Ryan]

... a code beautifier that forces the code to use coding standards ... made into a mandatory step in the plugin checklist, before plugins were added to the repository.

I think that would annoy far too many people.

It could be useful for core patches though I guess to make sure they're consistent.

[andreasnrb]

I mostly use FXCop and occassionaly some other stuff to check code quality with my C# code. Checks for a bunch of things haven't found anything similar for PHP yet.
I use NAnt to manage my whole development cycle with C#, run tests, check this and that, all ok make release package etc.

[Jacob Santos]

One thing to note about most beautifiers is that by default they convert tabs to spaces, because most PHP accepted standards use spaces instead of tabs. You'd have to either hack the beautifier or set the option to not do that, since some realize that not every project is going to use spaces.

Furthermore, you have the whole issue of rewriting keywords to constants, such as TRUE, FALSE, and NULL, which are technically constants within PHP and confusingly are also type keywords.