<?php

  /**
   * Calculates the sum for a particular column in a multidimensional array.
   *
   * @param array $array
   *   Input array.
   * @param string $key
   *   The key for which sum should be calculated.
   */
  protected function sumArrayColumn(array $array, string $key) {
    return array_reduce($array, function ($reduced, $item) use ($key) {
      $reduced += (int) $item[$key];
      return $reduced;
    });
  }