phroute VS TacticalTome

The router code for this could look like (using Phroute for the example). The functions could be sent to classes if you have that setup.

Finally, add a router to map all of this out. You could use a library, some one noted FastRoute, there a few out there like Phroute for one.

How hard did you look? There are plenty out there. FastRoute, Phroute, based on FastRoute, with basic middleware, League/Route - routing with middleware, using FastRoute, PSR 7 & 15, Slim Framework, at it's core, it like League/Route, etc. None of these require a full framework to use.

Using a router library like FastRoute or Phroute to show the example

Someone mentioned FastRoute. You can look at Phroute as well - https://github.com/mrjgreen/phroute

Additionally, you lose the checks at the top of those files (here' and here if you implement middleware. Here is one example using pretty URLs and a router library. Using Phroute to show the example - pseudo code to illustrate:

Using Phroute to show the example

This can be refactored. If you use start using a router and middleware, this can be done as middleware (or a before/after filter for older libraries - See the Filter Group section on this library for example usage - https://github.com/mrjgreen/phroute)

a) Structure your code base better. ie Your PHP code should be outside of the webroot. You can also group functionality, your project is a key example of where this can work - https://github.com/TacticalTome/TacticalTome/blob/e29eb11e8b12f4a2f538c8098ac16953665758bc/system/controllers/api.php