我可以将 PHP 对象传递给同一对象的构造函数吗？

Question

（所以结束了我之前的问题，所以这次我会尽量说得更清楚）当我运行在浏览器中输入以下代码时：

<?php
class MyNode {
    public $name;
    public $children = array();
    public $parent;

    public function __construct(string $name, $parent) {
        echo "in constructor\n";
      $this->name = $name;
      echo "name: " . $this->name . ".\n";
      $this->parent = $parent;
      #$this->parent = &$parent;
      echo "parent: " . $this->parent . ".\n";
    }
}
$RootNode = new MyNode("Root", null);
echo "done root x\n";
#$ChildNode = new MyNode("Child1", null);
$ChildNode = new MyNode("Child1", $RootNode);
echo "done child\n";
?>

浏览器打印“in constructor name: Root.parent: . done root x in constructor name: Child1.”然后因错误（在开发人员控制台中）“500（内部服务器错误）”而停止。如果我使用传递 null 而不是 $RootNode 的行（上面注释），它会成功。

将 $RootNode 传递给 MyNode 构造函数的正确方法是什么？

Answer 1

你非常接近 - if you had error reporting on，问题会很清楚。您的代码在尝试打印 $this->parent 时发出错误，因为 PHP 无法将 MyNode 的实例转换为字符串 - PHP 需要这样做才能打印它。

Here's an example of your code. 它发出此错误：

Fatal error: Uncaught Error: Object of class MyNode could not be converted to string in /in/T7Os5:12
Stack trace:
#0 /in/T7Os5(18): MyNode->__construct('Child1', Object(MyNode))
#1 {main}
  thrown in /in/T7Os5 on line 12

我建议实施 __toString() method (example):

<?php
class MyNode {
    public $name;
    public $children = array();
    public $parent;

    public function __construct(string $name, $parent) {
      echo "in constructor\n";
      $this->name = $name;
      echo "name: " . $this->name . ".\n";
      $this->parent = $parent;
      echo "parent: " . $this->parent . ".\n";
    }
    
    public function __toString()
    {
        return $this->name;
    }
}

$RootNode = new MyNode("Root", null);
echo "done root x\n";
$ChildNode = new MyNode("Child1", $RootNode);
echo "done child\n";

我可以将 PHP 对象传递给同一对象的构造函数吗？

Can I pass a PHP object to a constructor for that same object?

php

constructor

class

object