Functional Programming in PHP

functional_programming.php

<?php

$accumulator = function (
  string $accumulated_string, 
  string $mapped_list_element
) {
  return $accumulated_string . $mapped_list_element . "\n";
};

$mapped_array = array_reduce(
  array_map(
    function (int $list_element): string {
      return "A list element: " . $list_element;
    }, 
    [1, 2, 3, 4]
  ), 
  $accumulator,
  ""
);
echo $mapped_array;

$filtered_array = array_reduce(
  array_filter(
    [1, 2, 3, 4],
    function (int $list_element): bool {
      return $list_element > 2;
    }
  ),
  $accumulator,
  ""
);
echo $filtered_array;