如何在PHP中初始化构造函数中的变量

我正在编写这个简单的代码,不知道构造函数的问题是什么：

class Animal {
    public $_type;
    public $_breed;

    public function __construct ($t, $b) {
        echo "i have initialized<br/>";

        $this ->_type = $t; 
        $this ->_breed = $b;
        echo "type is " .$_type. "<br/>";

        echo "breed is " .$_breed. "<br/>";
    }

    public function __destruct () {
        echo "i am dying";
    }
}

$dog = new Animal("Dog", "Pug");

解决方法:

试试这个(注意回声线)：

class Animal {
    public $_type;
    public $_breed;

    public function __construct ($t, $b) {
        echo "i have initialized<br/>";

        $this->_type = $t; 
        $this->_breed = $b;

        //You have to use '$this' keyword to access
        //class attibutes:
        echo "type is " . $this->_type . "<br/>";
        echo "breed is " . $this->_breed . "<br/>";
    }

    public function __destruct () {
        echo "i am dying";
    }
}