如何从二维关联数组中取消设置/删除项目

Question

On sound advice from this Forum, I am re-writing code involving multi-dimensional array SESSIONS cart so that the product ID is the array name (I think I am explaining this correctly). I can add to the array, but I cannot remove anything. I am using an array to add new item data to the SESSIONS array. The code below represents a test adding items to the array and finally trying and failing to delete one. Any assistance in finding my errors is appreciated.

echo '**************  STEP ONE **********************';
// Initialize array    
$_SESSION['cart'] = array();

// Array of newitem
$id = 181;
$newitem = array(
    $id => array(
        'quantity' => 1,
        'part_number' => '600N5630-501',
    )
);
// Add newitem to cart
$_SESSION['cart'][] = $newitem;
// Display cart array with one item
var_dump($_SESSION['cart']);


echo '**************  STEP TWO **********************';

// Array of newitem
$id = 33;
$newitem = array(
    $id => array (
        'quantity' => 1,
        'part_number' => '369A7170-11',
    )
);
// Add newitem to cart
$_SESSION['cart'][] = $newitem;
// Display cart array with two items
var_dump($_SESSION['cart']);


echo '**************  STEP THREE **********************';

// Array of newitem
$id = 34;
$newitem = array(
    $id => array (
        'quantity' => 1,
        'part_number' => '369A7171-15',
    )
);
// Add newitem to cart
$_SESSION['cart'][] = $newitem;
// Display cart array with three items
var_dump($_SESSION['cart']);


echo '**************  STEP FOUR **********************';

// Unset by ID
$id = 34;
unset($_SESSION['cart'][$id]);
// Display cart array with two items
var_dump($_SESSION['cart']);

Answer 1

When you use $_SESSION['cart'][] it adds a new array item dynamically with the next index. You are then adding another two arrays under that one. Try creating the index with the specific $id :

$id = 181;
$newitem = array(
           'quantity' => 1,
           'part_number' => '600N5630-501',
);
// Add newitem to cart
$_SESSION['cart'][$id] = $newitem;

Alternately you could add/replace them like this:

$id = 181;
$newitem = array(
    $id => array(
        'quantity' => 1,
        'part_number' => '600N5630-501',
    )
);
// Add newitem to cart
$_SESSION['cart'] = array_replace($_SESSION['cart'], $newitem);