construct() 和 destruct()

__construct() 是 PHP 中最常用的魔術方法，因為它用於在初始化時設定類。與 __construct() 方法相反的是 __destruct() 方法。當沒有對你建立的物件的引用或強制刪除時，將呼叫此方法。PHP 的垃圾收集將通過首先呼叫其解構函式然後從記憶體中刪除它來清理物件。

class Shape {
    public function __construct() {
        echo "Shape created!\n";
    }
}

class Rectangle extends Shape {
    public $width;
    public $height;

    public function __construct($width, $height) {
        parent::__construct();

        $this->width = $width;
        $this->height = $height;
        echo "Created {$this->width}x{$this->height} Rectangle\n"; 
    }

    public function __destruct() {
        echo "Destroying {$this->width}x{$this->height} Rectangle\n";
    }
}

function createRectangle() {
    // Instantiating an object will call the constructor with the specified arguments
    $rectangle = new Rectangle(20, 50);

    // 'Shape Created' will be printed
    // 'Created 20x50 Rectangle' will be printed
}

createRectangle();
// 'Destroying 20x50 Rectangle' will be printed, because
// the `$rectangle` object was local to the createRectangle function, so
// When the function scope is exited, the object is destroyed and its
// destructor is called.

// The destructor of an object is also called when unset is used:
unset(new Rectangle(20, 50));