PHP面向对象程序设计__tostring()和__invoke()用法分析

<?php
ini_set('display_errors', 1);
class A{
  public $name;
  public $age;
  public $sex;
  function __construct($name, $age, $sex){
    $this->name = $name;
    $this->age = $age;
    $this->sex = $sex;
  }
}
$obj1 = new A('张三', 15, '男');
echo $obj1;  //echo 后面为字符串，而对象不是字符串，会报错
$v1 = "abc" . $obj1; //.为字符串连接符，会报错
$v2 = "abx" + $obj1; //+为加法运算符，会报错
?>

<?php
ini_set('display_errors', 1);
class A{
  public $name;
  public $age;
  public $sex;
  function __construct($name, $age, $sex){
    $this->name = $name;
    $this->age = $age;
    $this->sex = $sex;
  }
  function __tostring(){
    $str = "姓名" . $this->name;
    $str .= "年龄" . $this->age;
    $str .= "，性别" . $this->sex;
    return $str;  //这里可以返回“任何字符串内容”
  }
}
$obj1 = new A('张三', 15, '男');
echo $obj1;  //调用__tostring(),不会报错
?>

class A{
  function __invoke(){
    echo "<br />我是一个对象呀，你别把我当作一个函数来调用啊！";
  }
}
$obj = new A();
$obj();  //此时就会调用类中的方法__invoke()