code: public static function keyBy( $array, $index ) {
          $newArray = array();
          foreach( $array as $item ) {
              $key = \UArray::getKeyValue( $item, $index, 'empty' );
              $newArray[$key] = $item;
          }
          return $newArray;
      }
docs: ***********************************************************************
  GROUP METHODS
  ***********************************************************************