Reset option tag value with one from database using PHP MySQL

Initially I am populating my option tag with Quantity available in stock.

<select name="quantity" class="form-control input-sm" id="quantity">
    <?php for ($i=1; $i<=$Quantity; $i++) { ?>
    <option value="<?php echo $i;?>"><?php echo $i;?></option>
    <?php } ?>
</select>

I am updating Quantity from my html form using Javascript:

function update_id(id)
{
    if (confirm('Update quantity for this Item?')) {
        uid = id;
        quantity = $('select[name=quantity]').val()
        window.location.href="Cart.php?update_id="+uid+"&quantity="+quantity;//+'?quantity='+quantity;
    }   
}

and storing it in Cart table against that particular product. On reloading or refreshing the page, option tag gets reset to default value here as '1'. I want to assign option tag value with the Updated Quantity from DB against that particular product.

Screenshot of the cart

Thanks in Advance