Mas, numpang tanya, mungkin bs dibantu problem saya.

Jadi saat order di approve oleh admin, maka data pada stok barang akan dikurangi dengan semua kuantitas barang di database.

Ada 3 table.
tbl_barang
id | Nama_barang | Stok
1 | Barang A | 10
2 | Barang B | 10
3 | Barang C | 10
4 | Barang D | 10

tbl_order
id | kode_order
1 | ABCDE

tbl_order_detail
id | id_order |id_barang | qty
1 | 1 | 2 | 5
2 | 1 | 3 | 5
3 | 1 | 4 | 5

Jadi dalam 1 form, ada submit, saat ditekan, maka akan mengurangi semua stok sesuai tbl_order_detail.
Kira2 gimana model formnya sama proses saat di submitnya ya mas.
Pake

if($_POST}{

//proses

}

echo "<form action='' method='post'">;
$sql=mysql_query("SELECT * FROM blablabla inner join blablabala dst ");
while($sql=mysql_fetch_array($sql)){
echo "Anda memesan $data[nama_barang] sebanyak $data[qty]";
}
echo "<input type='submit' name='submit' value='Submit'/>";
echo "</form>";

if($_POST['submit']}{
foreach($_POST['item'] as $idBarang => $qty){
	$sql = "update tbl_barang set Stok=Stok-$qty where id='$idBarang'";
	mysql_query($sql);
}
}

echo "<form action='' method='post'">;
$sql=mysql_query("SELECT * FROM tbl_order_detail o inner join tbl_barang b on o.id_barang=b.id where id_order='1'");//silahkan diganti
?>
<table>
<?php
while($data=mysql_fetch_array($sql)){
?>
<tr>
<td><input type="checkbox" name="item[<?php echo $data['id_barang']?>]" value="<?php echo $data['qty']?>"/></td>
<td><?php echo $data['Nama_barang']?></td>
<td><?php echo $data['qty']?></td>
</tr>
<?php
}
?>
</table>
<?php
echo "<input type='submit' name='submit' value='Submit'/>";
echo "</form>";