<?php
class Cart {
    var $items;  // Objetos en nuestro carrito de compras
 
    // Agregar $num artículos de $artnr al carrito
 
    function add_item($artnr, $num) {
        $this->items[$artnr] += $num;
    }
 
    // Sacar $num artículos de $artnr fuera del carrito
 
    function remove_item($artnr, $num) {
        if ($this->items[$artnr] > $num) {
            $this->items[$artnr] -= $num;
            return true;
        } elseif ($this->items[$artnr] == $num) {
            unset($this->items[$artnr]);
            return true;
        } else {
            return false;
        }
    }
}
?>

class Lock
{
    private $isLocked = false;
 
    public function unlock()
    {
        $this->isLocked = false;
        echo 'You unlocked the Lock';
    }
    public function lock()
    {
        $this->isLocked = true;
        echo 'You locked the Lock';
    }
    public function isLocked()
    {
        return $this->isLocked;
    }
}
 
$aLock = new Lock; // Create object from the class blueprint
$aLock->unlock();  // You unlocked the Lock
$aLock->lock();    // You locked the Lock