`getQueryString()` 메소드는 준비(prepared)된 쿼리를 문자열로 반환합니다.

INSERT INTO `user` (`name`, `email`, `country`) VALUES (?, ?, ?)

PHP는 데이터베이스로 열린 모든 명령문을 닫는 작업을 꽤 잘 수행하지만, prepare 명령문을 완료하면 `close()` 메소드를 사용하여 닫는 것이 좋습니다

Array
(
    [0] => stdClass Object
        (
            [idx] => 6
            [name] => test1
            [country] => KR
            [email] => test1@test.com
            [password] => 
            [created_at] => 
        )

    [1] => stdClass Object
        (
            [idx] => 7
            [name] => test2
            [country] => KR
            [email] => test2@test.com
            [password] => 
            [created_at] => 
        )

    [2] => stdClass Object
        (
            [idx] => 8
            [name] => test3
            [country] => KR
            [email] => test3@test.com
            [password] => 
            [created_at] => 
        )

    [3] => stdClass Object
        (
            [idx] => 9
            [name] => test4
            [country] => KR
            [email] => test4@test.com
            [password] => 
            [created_at] => 
        )

    [4] => stdClass Object
        (
            [idx] => 10
            [name] => test5
            [country] => KR
            [email] => test5@test.com
            [password] => 
            [created_at] => 
        )

    [5] => stdClass Object
        (
            [idx] => 11
            [name] => test6
            [country] => KR
            [email] => test6@test.com
            [password] => 
            [created_at] => 
        )

    [6] => stdClass Object
        (
            [idx] => 12
            [name] => test7
            [country] => KR
            [email] => test7@test.com
            [password] => 
            [created_at] => 
        )

    [7] => stdClass Object
        (
            [idx] => 13
            [name] => test8
            [country] => KR
            [email] => test8@test.com
            [password] => 
            [created_at] => 
        )

    [8] => stdClass Object
        (
            [idx] => 14
            [name] => test9
            [country] => KR
            [email] => test9@test.com
            [password] => 
            [created_at] => 
        )

    [9] => stdClass Object
        (
            [idx] => 15
            [name] => test10
            [country] => KR
            [email] => test10@test.com
            [password] => 
            [created_at] => 
        )

)