PHP MySql multi row update

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PHP

MySQL

Hi all,

I have two pages that I'm trying to convert to one. The original lets you enter the info and posts to the update page which in turn updates the DB.

I want all this to happen on the same page, but I think I'm having trouble as the page is not posting maybe??

Update multiple rows in mysql<br>

<?php
error_reporting(E_ALL);

mysql_connect("","","");
mysql_select_db("") or die("Unable to select database");

$sql = "SELECT  product_id, product_sku, product_name, product_in_stock, product_in_stock_cardiff FROM mik1vm_product";

$result = mysql_query($sql) or die($sql."<br/><br/>".mysql_error());

$i = 0;


?>
<table width="500" border="0" cellspacing="1" cellpadding="0">
<form name="form1" method="post" action="">
<tr>
<td>
<table width="500" border="0" cellspacing="1" cellpadding="0">


<tr>
<td align="center">Product Id</td>
<td align="center">SKU</td>
<td align="center">Name</td>
<td align="center">In Stock</td>
<td align="center">In Stock Cardiff</td>
</tr>
<?php
while ($products = mysql_fetch_array($result)){
?>


<tr>
<td align="center"><? $products['product_id']; ?><? echo $products['product_id']; ?></td>
<td align="center"><input name='product_sku' type="text" id="product_sku" value="<? echo $products['product_sku']; ?>"></td>
<td align="center"><input name="product_name" type="text" id="product_name" value="<? echo $products['product_name']; ?>"></td>
<td align="center"><input name="product_in_stock" type="text" id="product_in_stock" value="<? echo $products['product_in_stock']; ?>"></td>
<td align="center"><input name="product_in_stock_cardiff" type="text" id="product_in_stock_cardiff" value="<? echo $products['product_in_stock_cardiff']; ?>"></td>
</tr>
<?php
}
?>
<tr>
<td colspan="4" align="center"><input type="submit" name="Submit" value="Submit"></td>
</tr>
</table>
</td>
</tr>
</form>
</table>
<?php
// Update on submit...
if(isset($_POST['Submit']) && $_POST['Submit'] == 'Submit'){
	
	$size = count($_POST['product_id']);

$i = 0;
while ($i < $size) {
	$product_sku= $_POST['product_sku'][$i];
	$product_id = $_POST['product_id'][$i];
	
	$query = "UPDATE mik1vm_product SET product_sku = '$product_sku' WHERE product_id = '$product_id' LIMIT 1";
	mysql_query($query) or die ("Error in query: $query");
	echo "$product_sku<br /><br />Updated!<br /><br />";
	++$i;
}
}

mysql_close();
?>

I'm very new to PHP so please bear with me...

ERROR -
Notice: Undefined index: product_id in /home/itjustwo/public_html/test/test.php on line 58

Thanks.