In a post to his site Brandon Savage shares some of his thoughts about PHP package development and suggests how to figure out what versions of the PHP language it should support.

Everybody likes “the new hotness.” [...] Perhaps, then, it shouldn’t be so surprising that people get tremendously excited when a new version of PHP comes out. People look forward to the new features, whether they be the trailing commas in list() syntax or counting of non-countable objects.

[...] A new version of PHP can pose challenges to open source package maintainers. There are questions, like what is the minimum version we will support and how soon can we take advantage of the new features we’ve been waiting on? I want to offer up some thoughts, both as a package maintainer and a user of many open source packages.

He goes on to suggest that package authors should support down to the last currently supported version of the language (v5.6 at the time of this post). This allows users of the package that may be restricted and don't have the "new hotness" to keep using the package. He points out that this doesn't mean that you shouldn't use new features, just that older versions should be supported along with the newer ones for those depending on the package. He makes three suggestions as to how he thinks package maintainers should approach the issue:

• maintainers should feel comfortable in bumping up the requirement to the latest (in a major release)
• maintainers should also ensure that the support is still there for older versions that can't use the newer features
• maintainers should bump up this minimum version when it falls out of active support

Supporting old versions of a language isn’t fun and isn’t glamorous. But it’s important. It’s important because there’a segment of the population who can’t upgrade yet. It’s important to make components accessible to a larger, broader audience who is struggling to find best practices and use modern packages. And it’s important for those users who are tied to a legacy version, and are struggling to get upgraded. But it’s the right thing to do for the community.