On the Exakat blog there's a new post covering some of the impact that PHP versions have on codebases they've reviewed in the normal course of their product's analysis and the requirements of Open Source software.

With the upcoming PHP 7.3, the question of the next migration is back on our tables. We’ll hear a strange mix of begging to move to the new versions for features and security, mixed with a constant threatening that some old versions will soon be unmaintained or worse. Indeed, there is versions impact on PHP code bases.

Particular witnesses of that evolution are open source projects. They usually have to support a wide range of versions, and in the same time, are actively encouraged to use the newest features. It is a delicate work of balancing compatibility and progress.

To observe the way Open Source projects handle the evolution of PHP, we have audited 1977 Open source PHP projects, by linting them with PHP versions from 5.5 to 7.3. This taught us the impact of PHP on code, over a long period of coding. Let’s review them.

The post starts by talking about linting of PHP files (checking the syntax for issues but not executing the contents). It then shares some statistics about the number of Open Source projects that lint on every build and how it has trended over time. They also share some results on the age of packages that are in wide use, showing that the ration of "old code" to "young code" is surprisingly similar.