Php Admin Panel Hata

<?php 
                include 'baglan.php'; 
                if ($_POST=['kaydet']){ 
                $id=$_GET['id']; 
                $oku = mysql_query('SELECT * FROM musteri WHERE id="'.$id.'"'); 
                $yaz = mysql_fetch_array($oku); 
                extract ($yaz); 
               $duzenle=mysql_query("UPDATE musteri set firma='$firma', isim='$isim' ,soyisim='$soyisim' ,musteri='$musteri' ,telefon='$telefon' ,tc='$tc' ,urun_no='$urun_no',urun_siparis='$urun_siparis',hizmet_baslama='$hizmet_baslama',hizmet_bitis='$hizmet_bitis',domain_adi='$domain_adi',domain_baslama='$domain_baslama',domain_bitis='$domain_bitis',durum='$durum' where id='$id'"); 
                } 
                   
                  ?> 
   
                 <form name="duzenle" action="musteri.php" method="post"> 
                  <tr> 
                    <td><h5 class="box-title">Müşteri ID</h5></td> 
                    <td><?echo $id?></td> 
                  </tr> 
                   <tr>   
                    <td><h5 class="box-title">Firma</h5></td> 
                    <td><input type="text" class="form-control" name="firma" value="<?echo $firma?>"/></td> 
                  </tr> 
                  <tr>   
                    <td><h5 class="box-title">İsim</h5></td> 
                    <td><input type="text" class="form-control" name="isim" value="<?echo $isim?>"/></td> 
                  </tr> 
                  <tr>   
                    <td><h5 class="box-title">Soyisim</h5></td> 
                    <td><input type="text" class="form-control" name="soyisim" value="<?echo $soyisim?>"</td> 
                  </tr> 
                  <tr> 
                    <td><h5 class="box-title">Müşteri Numarası</h5></td> 
                    <td><input type="text" class="form-control" name="musteri" value="<?echo $musteri?>"/></td> 
                  <tr> 
                    <td><h5 class="box-title">Telefon Numarası</h5></td> 
                    <td><input type="text" class="form-control" name="telefon" value="<?echo $telefon?>"/></td> 
                  </tr> 
  				<tr> 
                    <td><h5 class="box-title">TC Kimlik No</h5></td> 
                    <td><input type="text" class="form-control" name="tc" value="<?echo $tc?>"/></td> 
                  <tr> 
                  <tr> 
                    <td><h5 class="box-title">Ürün No</h5></td> 
                    <td><input type="text" class="form-control" name="urun_no" value="<?echo $urun_no?>"/></td> 
                  </tr> 
                   <tr> 
                    <td><h5 class="box-title">Ürün Sipariş No</h5></td> 
                    <td><input type="text" class="form-control" name="urun_siparis" value="<?echo $urun_siparis?>"/></td> 
                  </tr> 
                  <tr> 
                    <td><h5 class="box-title">Başlangıç Tarihi</h5></td> 
                    <td><input type="text" class="form-control" name="hizmet_baslama" value="<?echo $hizmet_baslama?>"/></td> 
                  </tr> 
                  <tr> 
                    <td><h5 class="box-title">Bitiş Tarihi</h5></td> 
                    <td><input type="text" class="form-control" name="hizmet_bitis" value="<?echo $hizmet_bitis?>"/></td> 
                  </tr> 
                  <tr> 
                    <td><h5 class="box-title">Domain Adı</h5></td> 
                    <td><input type="text" class="form-control" name="domain_adi" value="<?echo $domain_adi?>"/></td> 
                  </tr> 
                  <tr> 
                    <td><h5 class="box-title">Domain Başlama Tarihi</h5></td> 
                    <td><input type="text" class="form-control" name="domain_baslama" value="<?echo $domain_baslama?>"/></td> 
                  </tr> 
                  <tr> 
                    <td><h5 class="box-title">Domain Bitiş Tarihi</h5></td> 
                    <td><input type="text" class="form-control" name="domain_bitis" value="<?echo $domain_bitis?>"/></td> 
                  </tr> 
                  <tr> 
                    <td><h5 class="box-title">Durum</h5></td> 
                    <td> 
                      <select name="durum" class="form-control"> 
                          <option selected="selected" disabled="disabled">Lütfen Bir Değer Seçiniz</option> 
                          <option value="Aktif">Aktif</option> 
                          <option value="Pasif">Pasif</option> 
                          <option value="Beklemede">Beklemede</option> 
                    </select> 
                    </td> 
                  </tr> 
                  <tr> 
                    <td> 
                    </td> 
                    <td> 
                    <input type="submit" name="kaydet" value="Kaydet"/> 
                    </td> 
                  </tr> 
                </form> 
                </table></center> 
              </div>