php에서 mysql로그인 질문드립니다.

<?php
    $conn = mysqli_connect("localhost", "writer", 비번, "UserData");
 
    if($conn){ echo "Connection established"."<br>"; }
    else{ echo 'Cant connect: ' . mysqli_error($conn); die(); }
 
    $sql = "INSERT INTO User(userID, userPassword, userName) VALUES('ASDF1234', 'ABCDEFGH', '하윤')";
    $result = mysqli_query($conn, $sql);
 
    if($result) { echo "insert success!"; }
    else { echo 'failure: ' . mysqli_error($conn); }
 
    mysqli_close($conn);
?>