It appears that there’s no “trend” at all. All the frameworks are holding steady for searches on Google, except that Laravel is declining slightly. Laravel still holds the lion’s share of searches.
I didn’t include Silex because it’s in maintenance mode, and Lumen seems to be in a similar situation.
I thought, “maybe the excitement is in front end js frameworks.” Nope:
React is still increasing in popularity, and Angular is declining, but not by much. Vue holds steady.
So, Why Use Slim?
If Slim 4 isn’t the most popular framework, why should you use it?
It uses the PSR standard interfaces. So, your app’s somewhat future-proof, because your basic program organization follows standards.
For example, Slim 4 comes with the PSR-7 standard message interface. These are the Request and Response messages. Lumen uses Laravel’s, and requires a bridge (from Symfony) to convert messages to the standard. Symfony’s is also not PSR-7. Laminas uses PSR-7. Does it matter? Some people would say it doesn’t. It might matter if you want to use middleware components that are written for PSR-7.
However, that’s just one feature. Symfony and Laravel and Slim 4 use the PSR-11 standard dependency injection containers. So, they’re the same in that respect.
It has some flexibility in allowing you to choose libraries to integrate.
I dug around on Tech Empower, a benchmark site. Maybe I didn’t see trends because I’m looking for the wrong frameworks.
A bunch of frameworks are blowing past the better-known frameworks, at least on benchmarks. Some are familiar, based around Swoole, and some names are new to me, like KumbiaPHP and Ubiquity, and Swoole competitor Workerman. Some of these are like the old Twisted Python framework.
Slim is still faster than Laravel and Symfony, as expected.