teman-teman ketika tombol submit ditekan data tidak masuk ke database maupun tampilan form

tambah data

<!-- Modal body -->
                <form methode="POST" action="" enctype="multipart/form-data">
                    <section class="base">
                <div>
                    <p>Nama Dokter</p>
                    <input type="text" name="username" class="form-control">
                    <p>Email</p>
                    <input type="text" name="email" class="form-control">
                    <p>Alamat</p>
                    <input type="text" name="alamat" class="form-control">
                    <p>Nomor Telephone</p>
                    <input type="number" name="no_hp" class="form-control">
                    <button type="submit" class="btn btn-primary" name="addnew">Submit</button>
                </div>
                </form>

function

<?php
include "mysql_mysqli.inc.php";
session_start();

//koneksi
$conn = mysqli_connect("localhost","root","","db_komkordik");
if(mysqli_connect_errno()) {
    echo mysqli_connect_error();
}

function base_url($url = null) {
    $base_url = "http://localhost/komkordik";
    if($url != null) {
        return $base_url."/".$url;
    } else {
        return $base_url;
    }
}

//TAMBAH DATA
if(isset($_POST['addnew'])){
    $username      = $_POST['username'];
    $email         = $_POST['email'];
    $alamat        = $_POST['alamat'];
    $no_hp         = $_POST['no_hp'];

    $addtotable = mysqli_query($conn, "insert into kom_dokter (username,email,alamat,no_hp)
    values ('$username','$email','$alamat','$no_hp')");
    if($addtotable){
        header('location:index.php');
    } else {
        echo 'Gagal';
        header('location:index.php');
    }
}

?>