php对象 构造方法的使用

<?php
class Stu
{
    private $name;//项目中变量的值都是外部传过来的
    private $age;
    private $salary;

    public function __construct($name2,$age2,$salary2)  //构造方法初始化,只要new就先执行
    {
        $this->name = $name2;
        $this->age  = $age2;
        $this->salary = $salary2;
    }
    public function info()
    {
        echo '姓名是'.$this->name.'年龄是'.$this->age.'工资是'.$this->salary;
    }
}
 $obj = new Stu('明哥','29',3000);
 $obj -> info();