public function update($table, $data, $where, $conjunction = 'AND'){
        $values = array_merge(array_values($data),array_values($where));
        $keys = array_keys($data);
        $pairs = Array();
        foreach($keys as $key){
            $pairs[] = "{$key}=?";
        }//foreach
        $pairs = implode(',',$pairs);

        $keys = array_keys($where);
        $condition = Array();
        foreach($keys as $key){
            $condition[] = "{$key}=?";
        }//foreach
        $condition = implode(" {$conjunction} ",$condition);

        return $this->query($this->set("UPDATE {$table} SET {$pairs} WHERE {$condition}",$values));

    }