I have a login form in html, php, css languages. I want to browser to ask me automaticly to save the username and password. But it is not working. I am singin in the portal but i can not save the username and password.

My codes like that:

    <?php
    if ($_POST and !empty($_POST['username']) and !empty($_POST['password'])) {
        $sifre = $_POST['password'];
        $AD = $_POST['username'];
        $kontrol = $db2->query("SELECT * FROM Firma WHERE Kod = '$AD' and Parola = '$sifre' ")->fetch(PDO::FETCH_ASSOC);
        if ($kontrol) {
            $_SESSION['admin']['login'] = 1;
            $_SESSION['admin']['id'] = $kontrol['ID'];
            $_SESSION['admin']['Firma_Adi'] = $kontrol['Firma_Adi'];
            $_SESSION['admin']['Tur'] = $kontrol['Tur'];
            $_SESSION['admin']['kod'] = $kontrol['Kod'];
            $_SESSION['admin']['yetkili'] = $kontrol['Yetkili'];
            $_SESSION['admin']['plasiyer'] = $kontrol['PlasiyerID'];
            /* ?><script>Swal.fire( 'Giriş İşlemi Başarılı', 'Başarıyla giriş yaptınız, 1 saniye içerisinde yönlendiriliyorsunuz.', 'success' );</script><?php */
            header('refresh: 0; url=' . $site . 'ozet');
        } else {
            ?>
            <script>Swal.fire('Hata', 'Kullanıcı adı veya şifrenizi kontrol ediniz.', 'error');</script><?php
        }
    }
    ?>

    <form action="" method="post" autocomplete="on" >
                                                    
                                                <div class="form-group">        
                                                    <input type="text" id="username" name="username" autocomplete="username" class="form-control"
                                                            placeholder="Kullanıcı Adı"  required>
                                                            
                                                    </div>  
                                                
                                                <div class="form-group">
                                                    
                                                            <input type="password" id="password" name="password" autocomplete="current-password" class="form-control"
                                                            placeholder="Şifre" required>
                                                            
                                                </div>  
                                                
                                                <div class="form-group">
                                                    <button type="submit" class="btn btn-main-primary btn-block">Giriş
                                                        Yap</button>
                                                    </div>  
                                                </form>

I tried autocomplete but it is not working. And I add form action”index.php” it is also not working. When i add action the page is not works correctly.