PHP has a built in debugging and testing tool called assertions, which is essentially the assert() function and a few configuration options.

With this feature you can add additional checks to your application whilst you are developing it so that when you deploy to production you can be sure that things will run correctly. It is simple to run and allows you to embed testing code within your production code without having an adverse effect on performance.

Read more here: https://www.hashbangcode.com/article/debugging-and-testing-php-assert