construct() 和 destruct()

__construct() 是 PHP 中最常用的魔术方法，因为它用于在初始化时设置类。与 __construct() 方法相反的是 __destruct() 方法。当没有对你创建的对象的引用或强制删除时，将调用此方法。PHP 的垃圾收集将通过首先调用其析构函数然后从内存中删除它来清理对象。

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));