PHP 构造函数

<?php
    class Example
    {
        public function __construct()
        {
            echo "Hello lidihuo";
        }
    }
    $obj = new Example();
    $obj = new Example();
?>

<?php
    class demo
    {
        public function demo()
        {
            echo "constructor1...";
        }
    }
    
    class demo1 extends demo
    {
        public function __construct()
        {
            echo parent::demo();
            echo "constructor2...";
        }
    }
    $obj= new demo1();
?>