code: private function getAdministratorsArrayKeyForId(array $administratorsArray, int $id): ?int 
      {
          foreach ($administratorsArray as $key => $administrator) {
              if ($administrator['id'] == $id) {
                  return $key;
              }
          }
  
          return null;
      }
docs: /* returns key of results array for matching 'id' key, null if not found
  note, careful when checking return value as 0 can be returned (evaluates to false)