class - Creating a PHP checkout system -

i'm trying create fairly simple php checkout system.

the table of information i'm using is:

product code        name            price
       sw1              sandwich         £3.11
       cl1               chocolate        £5.00
       cf1                 coffee           £11.23

code is:

class product {     public $name;     public $price;      public function __construct($name, $price) {         $this->item = $name;         $this->price = $price;   } } class checkout {     protected $shopping_cart;      public function scan(product $product) {         $shopping_cart[] = $product;     }      public function total() {     // goes through shopping cart , sums price of contents         return array_reduce(             $this->shopping_cart,             function($total, $item) {                 return $total + $item->price;             },             0         );     } }  $pay = new checkout(); $pay->scan(new product("sandwich", 3.11)); $pay->scan(new product("chocolate", 5)); $pay->scan(new product("coffee", 11.23)); $price = $pay->total(); 

i'd add pricing rule items. example, i'd sandwiches buy-one-get-one-free , chocolates have bulk purchase discount. not sure if it'd work, i'm thinking should add this:

$sw1 = new checkout("sandwich", 3.11); $cl1 = new checkout("chocolate", 5); $cf1 = new checkout("coffee", 11.23);  if(scan($sw1 % 2 == 0)) {     $price = $price / 2; } elseif(scan($sw1 == 1)) { } else {     $price = $price / 2 + $price; }  if(scan($cl1 >= 3 && $cl1 % 3 == 0)) {     $price = $price - .50; } else { // insert logic make sure purchases include more 3 items, though not divisible 3, discounted accordingly. } 

appreciated. if knows how test code, that'd great ☺.

i create 'discount' interface can applied product and/or checkout. example:

interface idiscount {   public function apply(&$amount); }  class discount_halfoff implements idiscount {   public function apply(&$amount) {     $amount /= 2;   } }  class discount_fixedamount implements idiscount {   private $amount;    public function __construct($amount) {     $this->amount = $amount;   }    public function apply(&$amount) {     $amount -= $this->amount;   } }  class product {   private $discounts = [];    public function __construct($name, $price) {     $this->item  = $name;     $this->price = $price;   }    public function adddiscount(idiscount $discount) {     $this->discounts[] = $discount;   }    public function getprice() {     $price = $this->price;     foreach($this->discounts $discount)       $discount->apply($price);     return $price;           } }  class checkout {   private $contents  = [];   private $discounts = [];    public function adddiscount(idiscount $discount) {     $this->discounts[] = $discount;   }    public function scan(product $product) {     $this->contents[] = $product;   }    public function getcount() {     return count($this->contents);   }    public function gettotal() {     $ttl = 0;     foreach($this->contents $product)       $ttl += $product->getprice();      foreach($this->discounts $discount)       $discount->apply($ttl);      return $ttl;   } }  $sandwich = new product('sandwich', 3.11); $sandwich->adddiscount(new discount_halfoff());  $checkout = new checkout(); $checkout->scan($sandwich);  // logic included checkout class directly, depends on use case. if ($checkout->getcount() > 3) {   if ($checkout->getcount() % 3 == 0)     $checkout->adddiscount(new discount_fixedamount(0.50));   } else {     // insert logic make sure purchases include more 3 items, though not divisible 3, discounted accordingly.   } }  echo $checkout->gettotal() . "\n";