- array_map: documentation ( source)
- print_r: documentation ( source)
- array_keys: documentation ( source)
<?php
$array = [1, 2, 3, 4];
$callable = function($value, $key, array &$output) {
$output[$key] = $value * 100;
};
$output = [];
array_map($callable, $array, array_keys($array), $output);
print_r($output);