克隆（）

__clone 是使用 clone 关键字调用的。在实际克隆对象之后，它用于在克隆时操作对象状态。

class CloneableUser
{
    public $name;
    public $lastName;

    /**
     * This method will be invoked by a clone operator and will prepend "Copy " to the
     * name and lastName properties.
     */
    public function __clone()
    {
        $this->name = "Copy " . $this->name;
        $this->lastName = "Copy " . $this->lastName;
    }
}

例：

$user1 = new CloneableUser();
$user1->name = "John";
$user1->lastName = "Doe";

$user2 = clone $user1; // triggers the __clone magic method

echo $user2->name;     // Copy John
echo $user2->lastName; // Copy Doe