Maybe you've heard about Composer and how it makes working with PHP libraries and packages easier. There's lots of articles (besides the project documentation) that can help you get started but Rafael Dohms has just shared an excellent overview of versioning and the features the tool makes available to fine tune your requirements to just the right level.
I have been putting together a new talk about Composer, and that means looking around the community, doing loads of research and trying to identify the items that need to be covered in a talk. Mostly I have been trying to identify things that people do on a regular basis that according to composer internals is either wrong or not ideal. One such thing that I have found is the proper selection of versions, and that also led me to find a new feature in composer that makes everyone's life so much easier. So let me break this down.
He starts with a look at the selection of the actual version you'll need and how Composer treats each type of version match (strict vs wildcards vs a mix of the two). He shows an example of adding one of these version strings to a "composer,json" file, both manually and via a command line call.