Assignment: Method Overriding Practice

For this assignment, you'll take the class you created in the previous session and extend it with proper method overriding. The goal is to practice creating child classes that override parent methods in various ways.

Requirements:

1. Start with the simple class you created in the previous homework, or use the example class below.
2. Create at least two child classes that extend your original class.
3. In each child class, override at least two methods from the parent class.
4. Use different overriding approaches:
   • Complete replacement (new implementation)
   • Extension with parent:: call at the beginning
   • Extension with parent:: call at the end
   • Conditional parent:: call
5. Include proper documentation (PHPDoc comments) for each overridden method.
6. Create a test script that demonstrates the different behaviors of the parent and child classes.

Example Starting Class:

/**
 * Product class representing a basic product in an e-commerce system.
 */
class Product {
    protected $name;
    protected $price;
    protected $sku;
    protected $description;
    
    /**
     * Create a new product instance.
     *
     * @param string $name Product name
     * @param float $price Product price
     * @param string $sku Stock keeping unit
     * @param string $description Product description
     */
    public function __construct($name, $price, $sku, $description = '') {
        $this->name = $name;
        $this->price = $price;
        $this->sku = $sku;
        $this->description = $description;
    }
    
    /**
     * Get the product details as an array.
     *
     * @return array
     */
    public function getDetails() {
        return [
            'name' => $this->name,
            'price' => $this->price,
            'sku' => $this->sku,
            'description' => $this->description
        ];
    }
    
    /**
     * Calculate the final price including tax.
     *
     * @param float $taxRate The tax rate (0.1 for 10%)
     * @return float
     */
    public function calculatePriceWithTax($taxRate = 0.1) {
        return $this->price * (1 + $taxRate);
    }
    
    /**
     * Get formatted product information.
     *
     * @return string
     */
    public function getFormattedInfo() {
        return "Product: {$this->name} (SKU: {$this->sku}) - \${$this->price}";
    }
    
    /**
     * Check if the product is in a specific price range.
     *
     * @param float $minPrice Minimum price
     * @param float $maxPrice Maximum price
     * @return bool
     */
    public function isInPriceRange($minPrice, $maxPrice) {
        return $this->price >= $minPrice && $this->price <= $maxPrice;
    }
}
                

Starter Code for Child Classes:

/**
 * DigitalProduct extends the basic Product with digital-specific features.
 */
class DigitalProduct extends Product {
    protected $downloadUrl;
    protected $fileSizeInMB;
    
    /**
     * Create a new digital product instance.
     *
     * @param string $name Product name
     * @param float $price Product price
     * @param string $sku Stock keeping unit
     * @param string $description Product description
     * @param string $downloadUrl Download URL
     * @param float $fileSizeInMB File size in megabytes
     */
    public function __construct($name, $price, $sku, $description, $downloadUrl, $fileSizeInMB) {
        // Call parent constructor
        parent::__construct($name, $price, $sku, $description);
        
        // Set digital-specific properties
        $this->downloadUrl = $downloadUrl;
        $this->fileSizeInMB = $fileSizeInMB;
    }
    
    /**
     * {@inheritdoc}
     *
     * Override to include digital product specific details.
     */
    public function getDetails() {
        // TODO: Override this method to add digital-specific details
    }
    
    /**
     * {@inheritdoc}
     *
     * Override to use a different tax rate for digital products.
     */
    public function calculatePriceWithTax($taxRate = 0.05) {
        // TODO: Override this method to use digital-specific tax calculation
    }
}

/**
 * PhysicalProduct extends the basic Product with physical-specific features.
 */
class PhysicalProduct extends Product {
    protected $weight;
    protected $dimensions;
    protected $inStock;
    
    /**
     * Create a new physical product instance.
     *
     * @param string $name Product name
     * @param float $price Product price
     * @param string $sku Stock keeping unit
     * @param string $description Product description
     * @param float $weight Weight in kg
     * @param array $dimensions Array with width, height, depth
     * @param int $inStock Number of items in stock
     */
    public function __construct($name, $price, $sku, $description, $weight, $dimensions, $inStock) {
        // TODO: Call parent constructor
        
        // TODO: Set physical-specific properties
    }
    
    /**
     * {@inheritdoc}
     *
     * Override to include physical product specific details.
     */
    public function getFormattedInfo() {
        // TODO: Override this method to add physical-specific formatting
    }
    
    /**
     * {@inheritdoc}
     *
     * Override to also check stock availability.
     */
    public function isInPriceRange($minPrice, $maxPrice) {
        // TODO: Override this method to include stock check
    }
    
    /**
     * Calculate shipping cost based on weight and distance.
     *
     * @param float $distance Shipping distance in miles
     * @return float
     */
    public function calculateShippingCost($distance) {
        // Base rate + weight factor + distance factor
        return 5 + ($this->weight * 2) + ($distance * 0.1);
    }
}
                

Test Script Template:

// Include your class files
// require_once 'Product.php';
// require_once 'DigitalProduct.php';
// require_once 'PhysicalProduct.php';

// Create instances
$basicProduct = new Product('Basic Widget', 19.99, 'BW-001', 'A simple widget');
$ebook = new DigitalProduct('PHP Mastery', 29.99, 'E-BOOK-123', 'Learn PHP from scratch', 
                          'https://example.com/downloads/php-mastery.pdf', 15.5);
$chair = new PhysicalProduct('Office Chair', 149.99, 'CHAIR-456', 'Ergonomic office chair',
                           12.5, ['width' => 60, 'height' => 120, 'depth' => 65], 5);

// Test method overriding
echo "
Product Details Comparison:
";
echo "
";
print_r($basicProduct->getDetails());
echo "

";
print_r($ebook->getDetails());
echo "

";
print_r($chair->getDetails());
echo "
";

echo "
Price with Tax Comparison:
";
echo "Basic product: $" . number_format($basicProduct->calculatePriceWithTax(), 2) . "
";
echo "Digital product: $" . number_format($ebook->calculatePriceWithTax(), 2) . "
";
echo "Physical product: $" . number_format($chair->calculatePriceWithTax(), 2) . "
";

echo "
Formatted Info Comparison:
";
echo $basicProduct->getFormattedInfo() . "
";
echo $ebook->getFormattedInfo() . "
";
echo $chair->getFormattedInfo() . "
";

echo "
Price Range Check Comparison:
";
$minPrice = 20;
$maxPrice = 100;
echo "Basic product in range {$minPrice}-{$maxPrice}: " . 
     ($basicProduct->isInPriceRange($minPrice, $maxPrice) ? 'Yes' : 'No') . "
";
echo "Digital product in range {$minPrice}-{$maxPrice}: " . 
     ($ebook->isInPriceRange($minPrice, $maxPrice) ? 'Yes' : 'No') . "
";
echo "Physical product in range {$minPrice}-{$maxPrice}: " . 
     ($chair->isInPriceRange($minPrice, $maxPrice) ? 'Yes' : 'No') . "
";

// Test product-specific methods
echo "
Product-Specific Methods:
";
echo "Physical product shipping cost (100 miles): $" . 
     number_format($chair->calculateShippingCost(100), 2) . "
";
                

Bonus Challenges:

• Add a third child class SubscriptionProduct with a recurring billing feature
• Add a method to the parent class that calculates a discount, then override it in each child class with different discount strategies
• Add error checking and exception handling to the overridden methods
• Implement a final method in the parent class and explain why it shouldn't be overridden