search_api_location-8.x-1.0-alpha2/search_api_location.module

<?php

/**
 * @file
 * Adds location based search capabilities for Search API searches.
 */

/**
 * Returns an array of distance units.
 *
 * Distance searching is kilometer based, so all multipliers must be relative to
 * 1 kilometer.
 *
 * @return array
 *   An associative array with supported distance units and their
 *   specifications.
 */
function search_api_location_get_units() {
  $units = &drupal_static(__FUNCTION__);

  if (!isset($units)) {
    $units = [
      'km' => [
        'id' => 'km',
        'multiplier' => 1,
        'label' => 'Kilometers',
        'abbreviation' => 'km',
      ],
      'mi' => [
        'id' => 'mi',
        'multiplier' => 1.60935,
        'label' => 'Miles',
        'abbreviation' => 'mi',
      ],
    ];

    \Drupal::moduleHandler()->alter('search_api_location_units', $units);
  }

  return $units;
}