In this post on Medium.com Gediminas Rapolavicius provides a word of warning to those creating APIs (interfaces for tools, not like REST APIs) - "don't try to be too smart", favor consistency over cleverness.

When designing an API, it’s tempting to do a bit of extra work and surprise the developers using it. It might be returning some additional information that would require an additional call otherwise, or try to predict the intentions and handle some specific cases differently. The intentions are perfectly fine?—?provide a pleasant, simple interface.

The problem is that it requires making assumptions which, sometimes, are inevitably wrong. The worst case is when the API makes an assumption of what the developer expect to get back, gets it wrong, and returns something unexpected. More work with docs, more bug fixing.

He gives two examples of things he's encountered where the idea of the API was simple but assumptions made turned out to make things a bit more difficult: PHP's own array_rand function and WordPress' update_post_meta. He briefly covers each and explains that, while the intentions seemed good, the implementation was a bit confusing (and at times inconsistent), causing troubles when not functioning as expected.

Lukas Smith has a new post today about what he sees as an important part of PHP (or really most open source projects) - a predictable release cycle. It centers around the recent proposal to introduce the Zend Optimizer+ into the core and how it seems to be causing a delay with 5.5 (maybe up to 2 months).

What troubles me though is that its being proposed very late in the game for PHP 5.5, therefore causing a likely delay of 5.5 of at least about 2 months in the best case scenario if it were included. The other option of including it in 5.6 does not seem to be as popular at this point. This saddens me quite a bit since I believe that predictable release cycles would carry several advantages

He points out some things that come along with having predicability around the software releases like developers knowing when/if their changes will make it into the next release. It also makes it easier for end users to plan their releases of their own software, knowing when they'll be getting a feature. In this particular case, though, he doesn't quite understand the delay as the Zend Optimizer+ isn't a change to core, it's an addition:

What is even stranger for this case is that we are just talking about an extension here. Its not a language feature, there is no engine level integration. So even if its not added to core, people can easily get Optimizer+ via PECL. So in this case we are not talking about people having to wait another 10-11 months. Don't get me wrong I think getting an opcode cache into core is awesome, but the reality is that shared host users will probably still not have access to it [...] and the rest can still get it, albeit with a bit more effort.