how to visit the method in the child class from extends? - php

Question

Here I want to use the code class Child_Site extends Site to extend the class Site, and the class Site is used with the __construct to receive $par1, $par2. When I use
$D=new Child_Site("ddd","gggg");$D->getTitle(); to visit his parent class, it is totally fine. But when I want to visit the child method, why it give the error?
Fatal error: Uncaught ArgumentCountError: Too few arguments to
function Site::__construct(), 0 passed in
D:\phpstudy_pro\WWW\index.php on line 39 and exactly 2 expected in
D:\phpstudy_pro\WWW\index.php:7 Stack trace: #0
D:\phpstudy_pro\WWW\index.php(39): Site->__construct() #1 {main}
thrown in D:\phpstudy_pro\WWW\index.php on line 7
<?php
class Site {
var $url;
var $title;
function __construct( $par1, $par2 ) {
$this->url = $par1;
$this->title = $par2;
}
function setUrl($par){
$this->url = $par;
}
function getUrl(){
echo $this->url . PHP_EOL;
}
function setTitle($par){
$this->title = $par;
}
function getTitle(){
echo $this->title . PHP_EOL;
}
}
class Child_Site extends Site{
var $category;
function setCate($par){
$this->category=$par;
}
function getCate(){
echo $this->category.PHP_EOL;
}
}
$D = new Child_Site("ddd","gggg");
$D->getTitle();
$s = new Child_Site;
$s->setCate("xx");
$s->getCate();
?>