public function decrementByPk($primary_key, $keys, $step = 1)
    {
        if ($this->is_single) {
            return $this->incrementOrDecrementByPk($primary_key, $keys, $step, self::MINUS_NOTIFICATION);
        }
        return false;
    }
public function decrementByPk($primary_key, $keys, $step = 1)
    {
        if ($this->is_single) {
            return $this->incrementOrDecrementByPk($primary_key, $keys, $step, self::MINUS_NOTIFICATION);
        }
        return false;
    }
public function decrementByPk ( $ primary_key , $ keys , $ step = 1 ) { if ( $ this -> is_single ) { return $ this -> incrementOrDecrementByPk ( $ primary_key , $ keys , $ step , self :: MINUS_NOTIFICATION ) ; } return false ; }
Decrease key or keys by primary key

@param  $primary_key
@param  $keys
@param  int         $step
@return bool
Decrease key or keys by primary key