iletişim formu databse kaydetme

<?php
if($_POST[ok]){
$ac = fopen("dosya.txt","aw");

if(!$ac)
{
    echo "Hata !";
}

$adi = $_POST['adi'];
$email = $_POST['email'];
$tel = $_POST['tel'];
$konu = $_POST['konu'];
$aciklama = $_POST['aciklama'];

$eklenecek_metin = "$adi; $email; $tel; $konu; $aciklama\n";

fwrite($ac,$eklenecek_metin);
fclose($ac);
}
?> 



 <form action="" method="post">
          <div class="form-group">
            <label><b>Ad Soyad :</b></label>
            <input type="text"  name="adi" class="form-control" required>
          </div>
          <div class="form-group">
            <label ><b>E-Posta Adresiniz :</b></label>
            <input type="text" name="email" class="form-control" required>
          </div>
          <div class="form-group">
            <label><b>Telefon :</b></label>
            <input type="text" name="tel" class="form-control"  required="" />
          </div>
          <div class="form-group">
            <label ><b>Konu :</b></label>
            <input type="text" name="konu" class="form-control"  required="" />
          </div>
          <div class="form-group">
            <label><b>Mesaj :</b></label>
            <textarea name="aciklama" class="form-control" cols="30" rows="5" required></textarea>
          </div>
          <div class="form-group">
             <input type="submit" name="ok"  value="Gönder" class="btn btn-success"><br><br>
          </div>
        </form>