<?php
// in PHP arrow functions look like this

// long version required currently
function array_values_from_keys($arr, $keys) {
    return array_map(
      function ($x) use ($arr) { return $arr[$x]; }, // long
      $keys
    );
};

// with arrow functions
function array_values_from_keys($arr, $keys) {
    return array_map(
      fn($x) => $arr[$x], // short
      $keys
    );
}

// note the difference
$long  = function ($x) use ($arr) { return $arr[$x]; };
$short = fn($x) => $arr[$x];