How to unset / remove item from two dimensional associative array - php

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);