我不明白代码片段的用途

Question

在 Zend Frameword 2.5 中查看并看到一些代码，它工作正常但我的 IDE 显示错误。我不知道这段代码的目的。为什么要写：$this->table = clone $this->table;

Github Link: https://github.com/zendframework/zend-db/blob/master/src/TableGateway/AbstractTableGateway.php

函数：第 529-544 行

请解释一下。

public function __clone()
    {
        $this->resultSetPrototype = (isset($this->resultSetPrototype)) ? clone $this->resultSetPrototype : null;
        $this->sql = clone $this->sql;
        if (is_object($this->table)) {
            $this->table = clone $this->table;
        } elseif (
            is_array($this->table)
            && count($this->table) == 1
            && is_object(reset($this->table))
        ) {
            foreach ($this->table as $alias => &$tableObject) {
                $tableObject = clone $tableObject;
            }
        }
    }

Answer 1

我无法理解 Zend 的目的，但我希望在运行下面的两个代码片段之后，从不同的两个结果中，您可以理解

<?php
class A {
    public $foo = 1;
}  

class B {
    protected $value = 1;
    protected $bar = null;//
    public function __construct() {
      $this->bar = new A();
    }

    public function setValue($foo = 3){
      $this->value = $foo;
    }

    public function setFooBar($foo = 3){
      $this->bar->foo = $foo;
    }

    public function __clone() {
      $this->bar = clone($this->bar);
    }
}

$a = new B();
$c = clone($a);
$c->setFooBar(3);
$c->setValue(6);
var_dump($a);
echo "\n";
var_dump($c);
?>

<?php
class A {
    public $foo = 1;
}  

class B {
    protected $value = 1;
    protected $bar = null;//
    public function __construct() {
      $this->bar = new A();
    }

    public function setValue($foo = 3){
      $this->value = $foo;
    }

    public function setFooBar($foo = 3){
      $this->bar->foo = $foo;
    }
}

$a = new B();
$c = clone($a);
$c->setFooBar(3);
$c->setValue(6);
var_dump($a);
echo "\n";
var_dump($c);
?>

Answer 2

clone（或__clone）是一种所谓的魔术方法。查看 php 文档 on magic methods here.
以获取其他魔术方法的参考还要检查 the specific documentation for clone 他们在哪里解释了这个魔术方法的工作原理：

An object copy is created by using the clone keyword (which calls the object's __clone() method if possible). An object's __clone() method cannot be called directly.

换句话说，它允许您使用 public __clone 方法在其 class 定义中为对象实例定义自定义克隆行为。当您执行以下操作时，此方法将被调用 "magically"：

$clone = clone $instance;

我不明白代码片段的用途

I don't understand the purpose of code snippet

zend-framework2