PHP Resim güncelleme

Bir güncelleme sayfam var, bilgileri ayarlayıp güncelle dediğimde hepsi güncelleniyor fakar resim güncellemeyi yapamıyorum kodlar aşağıda nerede yanlış var acaba ?

bunlar güncelleme kodlarım:

if ((isset($_POST["MM_update"])) && ($_POST["MM_update"] == "form1")) {
  $updateSQL = sprintf("UPDATE urunler SET urun_ismi=%s, fiyat=%s, detaylar=%s, kategori=%s, altkategori=%s WHERE id=%s",
                       GetSQLValueString($_POST['urun_ismi'], "text"),
                       GetSQLValueString($_POST['fiyat'], "text"),
                       GetSQLValueString($_POST['detaylar'], "text"),
                       GetSQLValueString($_POST['kategori'], "text"),
                       GetSQLValueString($_POST['altkategori'], "text"),
                       GetSQLValueString($_POST['hiddenField'], "int"));

buda formum:

<form action="<?php echo $editFormAction; ?>" method="POST" enctype="multipart/form-data" name="form1" id="form1">
        <table width="100%">
          <tr>
            <td width="33%" height="30" align="right">Ürün İsmi:</td>
            <td width="67%" height="30"><label for="urun_ismi"></label>
            <input name="urun_ismi" type="text" id="urun_ismi" value="<?php echo $row_urungettir['urun_ismi']; ?>" /></td>
          </tr>
          <tr>
            <td height="30" align="right">Ürün Fiyatı:</td>
            <td height="30"><label for="fiyat"></label>
            <input name="fiyat" type="text" id="fiyat" value="<?php echo $row_urungettir['fiyat']; ?>" /></td>
          </tr>
          <tr>
            <td height="30" align="right">Kategori:</td>
            <td height="30"><label for="kategori"></label>
              <select name="kategori" id="kategori">
                <?php
do {  
?>
                <option value="<?php echo $row_katgetir['kat_id']?>"<?php if (!(strcmp($row_katgetir['kat_id'], $row_katgetir['kat_id']))) {echo "selected=\"selected\"";} ?>><?php echo $row_katgetir['kat_adi']?></option>
                <?php
} while ($row_katgetir = mysql_fetch_assoc($katgetir));
  $rows = mysql_num_rows($katgetir);
  if($rows > 0) {
      mysql_data_seek($katgetir, 0);
      $row_katgetir = mysql_fetch_assoc($katgetir);
  }
?>
            </select></td>
          </tr>
          <tr>
            <td height="30" align="right">Alt Kategori:</td>
            <td height="30"><label for="altkategori"></label>
              <select name="altkategori" id="altkategori">
                <?php
do {  
?>
                <option value="<?php echo $row_Recordset1['akat_id']?>"<?php if (!(strcmp($row_Recordset1['akat_id'], $row_Recordset1['akat_id']))) {echo "selected=\"selected\"";} ?>><?php echo $row_Recordset1['akategori']?></option>
                <?php
} while ($row_Recordset1 = mysql_fetch_assoc($Recordset1));
  $rows = mysql_num_rows($Recordset1);
  if($rows > 0) {
      mysql_data_seek($Recordset1, 0);
      $row_Recordset1 = mysql_fetch_assoc($Recordset1);
  }
?>
             </select></td>
          </tr>
          <tr>
            <td height="30" align="right">Ürün Detayı:</td>
            <td height="30"><label for="detaylar"></label>
            <textarea name="detaylar" id="detaylar" cols="45" rows="6"><?php echo $row_urungettir['detaylar']; ?></textarea></td>
          </tr>
          <tr>
            <td height="30" align="right">Ürün Resmi</td>
            <td height="30"><label for="fileField"></label>
            <input name="fileField" type="file" id="fileField" value="<?php echo $row_urungettir['resim']; ?>" /></td>
          </tr>
          <tr>
            <td height="30" align="right">&nbsp;</td>
            <td height="30"><input type="submit" name="button" id="button" value="Düzenle" />
            <input name="hiddenField" type="hidden" id="hiddenField" value="<?php echo $row_urungettir['id']; ?>" /></td>
          </tr>
        </table>
        <input type="hidden" name="MM_update" value="form1" />
      </form>