Composing functions in PHP

composefunctions.php

<?php



$sorted_arr = function ($range_to_sort) {
  // Annoyingly, PHP can't return the sorted array from a sort
  // Do it manually

  usort($range_to_sort, function ($a, $b)
  {
    return($a[0] > $b[0]);
  });

  return $range_to_sort;
};


$merge_ranges = function ($sorted_range) {
  return array_reduce($sorted_range, function ($accum, $event)
  {
    $len = count($accum) - 1;

    if ($event[0] <= $accum[$len][1]) {
      $start = $accum[$len][0];

      if ($event[1] <= $accum[$len][1]) {
        $end = $accum[$len][1];
      } else {
        $end = $event[1];
      }

      $accum[$len] = [$start, $end];

    } else {
      array_push($accum, $event);
    }
    return $accum;
  }, [$sorted_range[0]]);
};

$range_hours = function ($merged_range) {
  return array_reduce($merged_range, function($accum, $event)
  {
    array_push($accum, [$event[1] - $event[0]]);
    return $accum;
  }, []);
};

function compose(&$f, &$g) {
  // Functions could be large, let's pass byRef

  // We need to return a function
  return function() use($f, $g) {
    // When that new function is returned, arguments will be passed in
    // use func_get_args so that we can compose functions with unknown #s of args
    $args_in = func_get_args();
    // Now call our functions!
    return $g(call_user_func_array($f, $args_in));
  };
};

$cal = [[3, 4], [9, 12], [1, 3], [6, 8], [9, 10]];

$f = compose($sorted_arr, $merge_ranges);
$hours_taken = compose($f, $range_hours);

print_r($hours_taken($cal)); // [3, 2, 3]

?>