Online PHP editor | output for 35Ro5

<?php function mapCallback1($callback, $array){ $output = []; array_map(function($value) use ($callback, &$output) { $callback($value, function($value) use (&$output) { $output[] = $value; }); }, $array); return $output; } function mapCallback2($callback, $array){ $output = []; $push = function ($value) use (&$output) { $output[] = $value; }; foreach ($array as $value) { $callback($value, $push); } return $output; } $square = function ($x, $push) { $push($x * $x); }; var_dump(mapCallback1($square, [1, 2, 3])); var_dump(mapCallback2($square, [1, 2, 3]));