$inventory = [
['price' => 10.99, 'product' => 'foo 1'],
['price' => 5.99, 'product' => 'foo 2'],
['price' => 100, 'product' => 'foo 3'],
];
$price = array_column($inventory, 'price');
array_multisort($price, SORT_DESC, $inventory);
To PHP sort array by key, you should use:
ksort() (for ascending order) or krsort() (for descending order).
To PHP sort array by value, you will need functions:
asort() and arsort() (for ascending and descending orders).
ksort(array &$array, int $sort_flags = ?): int