php中_construct作用是什么php构造函数初始化对象逻辑

class User {<br>
    private $name;<br>
    private $age;<br>
<br>
    public function __construct($name, $age) {<br>
        $this->name = $name;<br>
        $this->age = $age;<br>
    }<br>
<br>
    public function getInfo() {<br>
        return "姓名：{$this->name}，年龄：{$this->age}";<br>
    }<br>
}<br>
<br>
$user = new User("张三", 25);<br>
echo $user->getInfo(); // 输出：姓名：张三，年龄：25

class Database {<br>
    private $host;<br>
    private $connection;<br>
<br>
    public function __construct($host = 'localhost') {<br>
        $this->host = $host;<br>
        $this->connect();<br>
    }<br>
<br>
    private function connect() {<br>
        // 模拟连接逻辑<br>
        echo "正在连接到 {$this->host}...";<br>
    }<br>
}

class Admin extends User {<br>
    private $role;<br>
<br>
    public function __construct($name, $age, $role) {<br>
        parent::__construct($name, $age); // 调用父类构造函数<br>
        $this->role = $role;<br>
    }<br>
}