public function where($id)
    {
        $this->validateIdentifier($id);

        if (!is_array($id)) {
            $key = reset($this->keys);
            return [$key => $id];
        } else {
            return $id;
        }
    }
public function where($id)
    {
        $this->validateIdentifier($id);

        if (!is_array($id)) {
            $key = reset($this->keys);
            return [$key => $id];
        } else {
            return $id;
        }
    }
public function where ( $ id ) { $ this -> validateIdentifier ( $ id ) ; if ( ! is_array ( $ id ) ) { $ key = reset ( $ this -> keys ) ; return [ $ key => $ id ] ; } else { return $ id ; } }
Creates the where condition for the identifier

@param int|string|array $id
@return array
Creates the where condition for the identifier