为什么数据没有插入数据库[重复]

Question

This question already has an answer here:

• “Notice: Undefined variable”, “Notice: Undefined index”, and “Notice: Undefined offset” using PHP 28 answers

I don't know what is wrong with this code. The data isn't inserting into the database.

       $connection = mysqli_connect('localhost', 'root', '', 'login-system');
if ($connection) {
    echo "everything works fine";
} else {
    echo "there is something wrong";
}
if (isset($POST['submit'])) {
    $username = $POST['username'];
    $password = $POST['password'];
    $query = "INSERT INTO users(username, password)";
    $query .= 'VALUES("$username", "$password")';
    $result = mysqli_query($connection,$query);
    if (!$result) {
    die('Query Failed'. mysqli_error());    
    }
}

Do you have any suggestion why this not working. Remember the server gets connected to database but not inserting data.

Thanks

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Answer 1

The problem is you are using $POST['submit'] which is wrong you need to use

$_POST['submit'] 

because php does not have any variable called $POST. Your full code should be like this.

include_once 'db.php';

if (isset($_POST['submit'])) {
    $username = $_POST['username'];
    $password = $_POST['password'];
    $query = "INSERT INTO users(username, password) VALUES('$username', '$password')";
    $result = mysqli_query($connection,$query);

    if (!$result) {
        die('Query Failed'. mysqli_error($connection));    
    }
}

NOTE: Your code is open to SQL injection attack you need to use prepared query.