Rewriting an anonymous function in php 7.4

Question

There is the following anonymous recursive function:

$f = function($n) use (&$f) {
    return ($n == 1) ? 1 : $n * $f($n - 1);
};

echo $f(5); // 120
         


        

Answer 1

I don't think you can rewrite the function as an arrow function.

An arrow function will capture the value of any external variables by value at the time the function is created. But $f won't have a value until after the function is created and the variable is assigned.

The original anonymous function solves this problem by capturing a reference to the variable with use (&$f), rather than use ($f). This way, it will be able to use the updated value of the variable that results from the assignment.