How to work with arrays of arrays (nested arrays/two-dimensional array)

Code that creates an array of arrays

$times_table = array(); // create an empty array
for ($i = 0; $i <= 12; $i++) {
  for ($j = 0; $j <= 12; $j++) {
    $times_table[$i][$j] = $i * $j;
  }
}

Code that adds values to the array of arrays

for ($i = 0; $i <= 12; $i++) {
  for ($j = 0; $j <= 12; $j++) {
    $times_table[$i][$j] = $i * $j;
  }
}

Code that refers to elements in the array of arrays

echo $times_table[4][3];
echo $times_table[7][6];

$times_table[4][3] = 12
$times_table[7][6] = 42

Code that creates a cart array

$cart = array();
$item['itemCode'] = 123;
$item['itemName'] = 'Visual Basic';
$item['itemCost'] = 57.5;
$item['itemQuantity'] = 5;
$cart[] = $item;
$item['itemCode'] = 456;
$item['itemName'] = 'Java';
$item['itemCost'] = 59.5;
$item['itemQuantity'] = 2;
$cart[] = $item; // add item array to cart array

$cart = Array ( [0] => Array ( [itemCode] => 123 [itemName] => Visual Basic [itemCost] => 57.5 [itemQuantity] => 5 ) [1] => Array ( [itemCode] => 456 [itemName] => Java [itemCost] => 59.5 [itemQuantity] => 2 ) )

Code that creates and adds another associative array to the cart array

$item = array(); // create an empty item array

Code that refers to the elements in the array of associative arrays

echo $cart[0]['itemCode']; // displays 123
echo $cart[1]['itemName']; // displays Java

$cart[0]['itemcode'] = 123
$cart[1]['itemcode'] = Java

A more concise way to create an array of arrays

$cart = array(
  array('itemCode' => 123, 'itemName' => 'Visual Basic', 'itemCost' => 57.5, 'itemQuantity' => 5),
    array('itemCode' => 456, 'itemName' => 'Java', 'itemCost' => 59.5, 'itemQuantity' => 2)
);

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