Question

How to use higher-order functions in PHP

Answer 1

// A higher‑order function is a function that does at least one of the following:
// 1. Takes another function as an argument
// 2. Returns a function as its result
// If it does either one, it qualifies.

// Higher-order function: takes a function as an argument
function applyTwice(callable $fn, int $x): int {
    return $fn($fn($x));
}

// A simple function to pass in
function add3(int $n): int {
    return $n + 3;
}

// Use the higher-order function
$result = applyTwice('add3', 5); // 5 + 3 = 8 + 3 = 11

echo $result . PHP_EOL;


/*
run:

11

*/

 

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