General
You should reconsider the naming of some methods. For example,
interface IComparable
{
public function equals($obj);
}
is more clear about what it really does (comments are omitted to save space; of course, proper DocBlock comments should always be included with your code). This w...
There is no reason for the cart to be a singleton (singleton is an Antipattern). On the other hand, the container property holds a reference to the cart data, so any cart provided with the same storage container will have identical data.
To use the cart, you instantiate it: $myCart = new Cart;. Then you can use it's methods: $myCart->clear();. Static methods are avoided, because they hamper testing. -- array_sum is not used, because the values are not in the same array (each item is again an array within the main array).
$this->container[] = &$entry; does not erase the array, but adds a reference to the new entry.
I do not know why, but I can not increment the quantity of an item. If I follow step by step the execution, I realize that this is the code that does not work: $entry['quantity']++; and $entry['quantity']--;.
The unary operator '--' is position dependent. In front of the variable, the increment is done before the assignment, and after the variable the increment is done after the assignment.
Discussion between nibra and Hugo Lap…
Discussion between nibra and Hugo Lap…