Ouzo\Utilities\Functions::identity PHP Метод

    public static function identity()
    {
        return function ($object) {
            return $object;
        };
    }

 /**
  * This method creates associative array using key and value functions on array elements.
  *
  * Example:
  * <code>
  * $array = range(1, 2);
  * $map = Arrays::toMap($array, function ($elem) {
  *      return $elem * 10;
  * }, function ($elem) {
  *      return $elem + 1;
  * });
  * </code>
  * Result:
  * <code>
  * Array
  * (
  *      [10] => 2
  *      [20] => 3
  * )
  * </code>
  *
  * @param array $elements
  * @param callable $keyFunction
  * @param callable|null $valueFunction
  * @return array
  */
 public static function toMap(array $elements, $keyFunction, $valueFunction = null)
 {
     if ($valueFunction == null) {
         $valueFunction = Functions::identity();
     }
     $keys = array_map($keyFunction, $elements);
     $values = array_map($valueFunction, $elements);
     return empty($keys) ? array() : array_combine($keys, $values);
 }