Multiple Rows Update with same form names in PHP - php

Question

I'm getting caught up on PHP again, and have the following update code. This works, but only for the last one inserted? I need to update for all gritem id's. I thought adding the [] to a form field that is not unique allows PHP to parse it as an array, but it still sees it as one field?
My HTML I have:
<input type="hidden" name="gritemid[]" value="<?PHP echo $row2['gritemid']; ?>">
<input type="text" name="grqty[]" id="grqty[]" value="" />
The Following PHP code
if(isset($_POST['storageloc']))
{
//Set the GRQTY to subtract from the Orderqty on each item in the list if selected
// find out how many records there are to update
$size = count($_POST['gritemid']);
// start a loop in order to update each record
$i = 0;
while ($i < $size) {
// define each variable
$gritemid= $_POST['gritemid'][$i];
$grqty= $_POST['grqty'][$i];
if ($grqty > "0") {
// do the update and print out some info just to provide some visual feedback
$query = "UPDATE gr_items SET orderqty = orderqty - $grqty WHERE gritemid = '$gritemid' LIMIT 1";
mysql_query($query) or die ("Error in query: $query");
}
++$i;
}
mysql_close();

Answer 1

First of all, you really should do some validation/sanitisation of your post vars before dropping them into a query. As both the vars you are using appear to be integers I would suggest using intval() -
// define each variable
$gritemid = intval($_POST['gritemid'][$i]);
$grqty = intval($_POST['grqty'][$i]);
If you replace your call to mysql_query() with print($query); do you see the multiple queries that you would expect?