商城SKU管理系統的功能實作：PHP程式編寫與最佳化技巧

<?php

class SKU
{
   private $skuId;
   private $productName;
   private $price;
   private $stock;
   private $attributes;

   public function __construct($skuId, $productName, $price, $stock, $attributes)
   {
      $this->skuId = $skuId;
      $this->productName = $productName;
      $this->price = $price;
      $this->stock = $stock;
      $this->attributes = $attributes;
   }

   // Getter and setter methods go here

   public function updatePrice($newPrice)
   {
      $this->price = $newPrice;
   }

   public function updateStock($newStock)
   {
      $this->stock = $newStock;
   }
}

class SKUManager
{
   private $skus;

   public function __construct()
   {
      $this->skus = array();
   }

   public function addSKU($sku)
   {
      $this->skus[] = $sku;
   }

   public function getSKUById($skuId)
   {
      foreach ($this->skus as $sku) {
         if ($sku->getSkuId() == $skuId) {
            return $sku;
         }
      }
      return null;
   }
}

// Usage example
$skuManager = new SKUManager();

$sku1 = new SKU(1, "Product 1", 10.99, 100, array("color" => "red", "size" => "M"));
$skuManager->addSKU($sku1);

$sku2 = new SKU(2, "Product 2", 19.99, 50, array("color" => "blue", "size" => "L"));
$skuManager->addSKU($sku2);

// Update price of SKU1
$sku1 = $skuManager->getSKUById(1);
$sku1->updatePrice(9.99);