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  • Update shopping cart by adding quantities together if the same product is chosen

This is the code that I'm using for a shopping cart in order to update the quantity if the same product id is chosen.

$cart_items is a two-dimensional session array composed of the id session array and the quantity session array. While looping through $cart_items, I create a temporary array $temp_array so that I can execute some logic on the array without changing the normal output. $temp_array is the $cart_items array without the last items which would be the $REQUEST id and the $REQUEST quantity. So the two $REQUESTs are popped off with array_pop and then the remaining $SESSIONs are compared to the $_REQUEST id with

$j = array_search($REQUEST["element_id$i"], $temp_array);
$j is now the key that corresponds to the id in $temp_array where the $_REQUEST id has been found.

if( $j==$temp_array[$i])

If $j is the key of the item in $temp_array, then the $_REQUEST is unset and the quantities for the item are added together.

There are two problems with this code. First of all the var_dump of the $temp_array is always an empty array but I am expecting to get an array with just the last element popped off. Secondly,
I get the error "Undefined offset" for the $i variable in this line of the code: if( $j==$temp_array[$i])


foreach($cart_items as $item) {
foreach($item["id"] as $key => $val) {
foreach($item["quantity"] as $i => $value) {
	if ($key == $i){
	
$temp_array = $cart_items;
$array = array_pop($temp_array);
var_dump($temp_array);

if (isset($_REQUEST["element_id_$i"]) && isset($_REQUEST["quantity_$i"])&& isset($value)){
	
$j = array_search($_REQUEST["element_id_$i"], $temp_array);
if( $j==$temp_array[$i]) {
echo "<b>SAME PRODUCT ADDED</b>";
$value += $_REQUEST["quantity_$i"];
unset($_REQUEST["element_id_$i"]);
}}}}}}
    foreach($cart_items as $item) {
	foreach($item["id"] as $key => $val) {
		foreach($item["quantity"] as $i => $value) {
			if ($key == $i){
				$temp_array = $cart_items;
				$array = array_pop($temp_array);
				var_dump($temp_array);

			if (isset($_REQUEST["element_id_$i"]) && isset($_REQUEST["quantity_$i"]) && isset($value)) {

				$j = array_search($_REQUEST["element_id_$i"], $temp_array);
				if( $j==$temp_array[$i]) {
					echo "<b>SAME PRODUCT ADDED</b>";
					$value += $_REQUEST["quantity_$i"];
					unset($_REQUEST["element_id_$i"]);
				}
			}
		}
	}
}
}

    As soon as I do that I can see just in the first four lines that you've got a whole loop going on that's not needed.

    foreach($cart_items as $item) {
	foreach($item["id"] as $key => $val) {

	$value = $item["quantity"][$key];

	$temp_array = $cart_items;
	$array = array_pop($temp_array);
	var_dump($temp_array);

	if (isset($_REQUEST["element_id_$i"]) && isset($_REQUEST["quantity_$i"]) && isset($value)) {

		$j = array_search($_REQUEST["element_id_$i"], $temp_array);
		if( $j==$temp_array[$i]) {
			echo "<b>SAME PRODUCT ADDED</b>";
			$value += $_REQUEST["quantity_$i"];
			unset($_REQUEST["element_id_$i"]);
		}
	}
}
}

    Still not clear how you've got things structured where you have to remove something that you presumably just added nanoseconds earlier (but somehow then lost making array_pop necessary because fortunately you know it's the last one added), but having the IDs and quantities in separate arrays looks like a hazard, since you have to do a lot of search back and forth between them to pair them up.

    I don't know what your $val is since it's unused here, but if it's not being at all, perhaps store the item quantities there instead of in a separate array. A one-dimensional $cart_items array that is a list of IDs and quantities, in other words:

    $cart_items = [
    10001 => 42,
    10002 => 17,
    10003 => 21,
    ....
    ];
    If you have to carry more information in the $cart_items array for each item:
    $cart_items = [
    10001 => ['quantity' => 42, 'more' => 'information', 'foo' => 'bar'],
    10002 => ['quantity' => 17, 'more' => 'information', 'foo' => 'baz'],
    10003 => ['quantity' => 21, 'more' => 'information', 'foo' => 'wibble'],
    ....
    ];

    For convenience that "more" information can include a repeat of the ID so that you can retrieve it from any given $cart_item element instead of having to search or guess.

    $cart_items = [
    10001 => ['id' => 10001, 'quantity' => 42, 'more' => 'information', 'foo' => 'bar'],
    10002 => ['id' => 10002, 'quantity' => 17, 'more' => 'information', 'foo' => 'baz'],
    10003 => ['id' => 10003, 'quantity' => 21, 'more' => 'information', 'foo' => 'wibble'],
    ....
    ];

      Wonder if things could be simplified by using array notation in the HTML form?

      // first item fields something like:
<input name="item[0][element_id]" type="...">
<input name="item[0][quantity]" type="...">
// next item just increments that first index:
<input name="item[1][element_id]" type="...">
<input name="item[1][quantity]" type="...">

      Seems like the resulting $_REQUEST['item'] array would then be much easier to traverse?

      NogDog Wonder if things could be simplified by using array notation in the HTML form?

      Good point. I saw those element_id_$i things there but didn't make the connection.

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