dev-php have packages that require >=php-5. Packages in dev-php5 require specific PHP versions in RDEPEND anyway because they do not work with all versions of PHP 5. Regarding pecl-packages, they have to be rebuilt on minor version upgrade because that is where the ABI break happens and it is more likely that users want to use multiple minor versions than only multiple major versions. Thus, categories do not make slotting simpler either. Having two categories for php-related packages does not serve any purpose. It is only confusing and it makes auto-generation of PEAR-based packages more difficult.
As said on IRC, I agree with your reasoning. As this is will require quite some reshuffling (pkg-moving), I'll get to it after I've handled the php-5.3 fallout.
Thanks. Sorry if it was inappropriate to file a bug about this, but I thought it would be useful to have this as a task somewhere public. I thought about writing this on the overlay wiki, but the wiki does not seem to be much in use.
5.3 fallout handled. We got slotting on our plate, so if it doesn't help with it, it's probably better to defer it until after that. But I'm sure I will get to it after slotting is out.
Merge has been done. If you have any issues with this (read: if I screwed up and there's still some mention of dev-php5 in the tree), please comment and/or reopen the bug. Thanks for the patience.
