One of the new features added to PHP 8.4 is a new attribute that will allow us to easily mark a function as deprecated in userland code. This will trigger a deprecation notice like when the built-in functions are deprecated so we can more easily find where our code has been deprecated (and others).

<?php
#[\Deprecated]
function test() {
}

// output: 
// Deprecated: Function test() is deprecated in ...
test();

Want to Know More?

I did a whole article for php[achitect] on fun new features in PHP 8.4 where I got into more details. It's also available in a video version if you're so inclined.