php login form page

<?php
define("DB_HOST", "mysql.dungla.com");
define("DB_USER", "dungla");
define("DB_PASS", "password");
define("DB_NAME", "2017_mukeshdak");
if($_SERVER["REQUEST_METHOD"]=="POST")
{
$username = $_POST["username"];
$password = $_POST["password"];
$connection = mysqli_connect(DB_HOST, DB_USER, DB_PASS, DB_NAME);
$query = "INSERT INTO login_users(username, password) ";
$query .= " VALUES('".$username."', '".$password."') ";
$result = mysqli_query($connection, $query);
if(!$result)
{
die("Query Failed !!!");
}
else
{
echo "Last insert id is : ".$connection->last_insert_id();
}
}
?>
<html lang="en">
    <head>
        <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css" >
    </head>
    <body>
        <div class="container">
            <div class="col-sm-6">
                <form action="login_create.php" method="POST">
                    <div class="form-group">
                        <label for="username">Username: </label>
                        <input type="text" name="username" class="form-control">
                    </div>
                    <div class="form-group">
                        <label for="password">Password: </label>
                        <input type="password" name="password" class="form-control">
                    </div>
                    <div class="form-group">
                        <input type="submit" name="submit" value="Submit" class="btn btn-primary form-control">
                    </div>
                </form>
            </div>
        </div>
    </body>
</html>