警告：mysqli_query（）期望参数1为mysqli，在第14行的C：\ wamp64 \ www \ Test \ php \ Register.php中给出null [关闭]

Question

I'm trying to create a registration system for my site and get the error:

( ! ) Warning: mysqli_query() expects parameter 1 to be mysqli, null given in C:\wamp64\www\Test\php\Register.php on line 14

php code:

session_start();
$db = mysqli_connect("localhost", "root", "", "users");
if(isset ($_POST['Register_btm'])) {
    $name = mysqli_real_escape_string($db, $_POST['name']);
    $email = mysqli_real_escape_string($db, $_POST["email"]);
    $username = mysqli_real_escape_string($db, $_POST["username"]);
    $password = mysqli_real_escape_string($db, $_POST["password"]);
    $password2 = mysqli_real_escape_string($db, $_POST["password2"]);

if($password == $password2)
    $password = MD5($password);
    $sql = "INSERT INTO users(id, name, email, username, pssword) VALUES ('null','$name','$email','$username','$pssword')";
    mysqli_query($dm, $sql);
    $_SESSION[message] = "You have successfully registered";
    $_SESSION[username] = $username;
}
else {
    @$_SESSION[message] = " Passwords do not match";
}
?>

What can I do?

Answer 1

You used $dm instead of $db, here corrected code -

    session_start(); 
    $db = mysqli_connect("localhost", "root", "","users");
    if(isset ($_POST['Register_btm'])) { 
    $name = mysqli_real_escape_string($db, $_POST['name']);
    $email = mysqli_real_escape_string($db, $_POST["email"]);
    $username = mysqli_real_escape_string($db, $_POST["username"]); 
    $password = mysqli_real_escape_string($db, $_POST["password"]); 
    $password2 = mysqli_real_escape_string($db, $_POST["password2"]); 
    if($password == $password2) $password = MD5($password);

    $sql = "INSERT INTO users(id, name, email, username, pssword) VALUES 
    ('null','$name','$email','$username','$pssword')"; 
    mysqli_query($db, $sql);

    $_SESSION[message] = "You have successfully registered"; 
    $_SESSION[username] = $username; 
    } else { 
    @$_SESSION[message] = " Passwords do not match";
    } 
    ?>