Question

我创建了一个简单的类来管理一个看起来很奇怪的树数据结构（要遵循的代码）。当我发现这不是我的错误时，我创建了一个同样令人费解的行为的测试用例。这与5.3和5.4相同。

这是我的测试用例：

<?php
class testcaseA {
    public function __construct($one=0, $two=1, $three=2) {
        $this->obj = new testcaseB($one++, $three, $two);
    }
    public function &get($what){
        return $this->obj->get($what);
    } 
}
class testcaseB {
    public function __construct($one, &$two, &$three) {
        $this->one=$one;
        $this->two=$two;
        $this->three=$three;
        echo "\$one={$one}";
    }
    public function &get($what){
        echo "<p>You asked for $what. $what ain't no country I ever heard of.<br />";
        echo "Check: [{$this->one}], {$this->two}, {$this->three}. Is this thing on?</p>";
        $this->obj[$what] = new testcaseB($this->one++,$this->two,$this->three);
        return $this->obj[$what];
    } 
}
ini_set('display_errors',1); 
error_reporting(E_ALL);
$bob = new testcaseA();
$bob->get("What")->get("Spam")->get("America");
$bob->get("What")->get("EU")->get("France");
echo "<pre>";
print_r($bob);

现在我预期的输出是看$ 1增量1,2,3,1,2,3的值并生成树形。

这是我实际获得的输出：

$one=0

You asked for What. What ain't no country I ever heard of.
Check: [0], 2, 1. Is this thing on?
$one=0

You asked for Spam. Spam ain't no country I ever heard of.
Check: [0], 2, 1. Is this thing on?
$one=0

You asked for America. America ain't no country I ever heard of.
Check: [0], 2, 1. Is this thing on?
$one=0

You asked for What. What ain't no country I ever heard of.
Check: [1], 2, 1. Is this thing on?
$one=1

You asked for EU. EU ain't no country I ever heard of.
Check: [1], 2, 1. Is this thing on?
$one=1

You asked for France. France ain't no country I ever heard of.
Check: [1], 2, 1. Is this thing on?
$one=1

testcaseA Object
(
    [obj] => testcaseB Object
        (
            [one] => 2
            [two] => 2
            [three] => 1
            [obj] => Array
                (
                    [What] => testcaseB Object
                        (
                            [one] => 2
                            [two] => 2
                            [three] => 1
                            [obj] => Array
                                (
                                    [EU] => testcaseB Object
                                        (
                                            [one] => 2
                                            [two] => 2
                                            [three] => 1
                                            [obj] => Array
                                                (
                                                    [France] => testcaseB Object
                                                        (
                                                            [one] => 1
                                                            [two] => 2
                                                            [three] => 1
                                                        )

                                                )

                                        )

                                )

                        )

                )

        )

)

这让我很困惑，但我想知道链式使用是否可能以我不期望的方式设置值。

所以我试过这个，我在前面的代码之后添加了：

...same classes and initial code as before...
$a=$bob->get("What");
$b=$a->get("Spam");
$c=$b->get("America");
//$bob->get("What")
$d=$a->get("EU");
$e=$d->get("France");  
print_r($bob);

这产生了一系列不同但仍然无法预测的结果。

You asked for What. What ain't no country I ever heard of.
Check: [2], 2, 1. Is this thing on?
$one=2

You asked for Spam. Spam ain't no country I ever heard of.
Check: [2], 2, 1. Is this thing on?
$one=2

You asked for America. America ain't no country I ever heard of.
Check: [2], 2, 1. Is this thing on?
$one=2

You asked for EU. EU ain't no country I ever heard of.
Check: [3], 2, 1. Is this thing on?
$one=3

You asked for France. France ain't no country I ever heard of.
Check: [3], 2, 1. Is this thing on?
$one=3testcaseA Object
(
    [obj] => testcaseB Object
        (
            [one] => 3
            [two] => 2
            [three] => 1
            [obj] => Array
                (
                    [What] => testcaseB Object
                        (
                            [one] => 4
                            [two] => 2
                            [three] => 1
                            [obj] => Array
                                (
                                    [Spam] => testcaseB Object
                                        (
                                            [one] => 3
                                            [two] => 2
                                            [three] => 1
                                            [obj] => Array
                                                (
                                                    [America] => testcaseB Object
                                                        (
                                                            [one] => 2
                                                            [two] => 2
                                                            [three] => 1
                                                        )

                                                )

                                        )

                                    [EU] => testcaseB Object
                                        (
                                            [one] => 4
                                            [two] => 2
                                            [three] => 1
                                            [obj] => Array
                                                (
                                                    [France] => testcaseB Object
                                                        (
                                                            [one] => 3
                                                            [two] => 2
                                                            [three] => 1
                                                        )

                                                )

                                        )

                                )

                        )

                )

        )

)

这仍然不是我追求的行为，但它更接近。我需要的是使用一串对象来遍历树（与第一种情况一样），一个指向值$ 2和$ 3的指针，在实际情况下是数组而不是交换。我不想做的是不必要地复制对象。

另一方面，我需要让所有对象共享一对他们都使用的变量。

我的猜测是，方法get()可以提供byval而不是byref，尽管本能地这似乎是错误的。

任何人都可以解释$one值的作用吗？

也可以有人帮我理解第一次测试用例的行为，尤其是第一次对数组中的值有什么影响吗？

更新

利用我们的测试用例现在看起来很棒的建议：

class testcaseA {
    public function __construct($one=0, $two=1, $three=2) {
        $this->obj = new testcaseB(++$one, $three, $two);
    }
    public function &get($what){
        return $this->obj->get($what);
    } 
}
class testcaseB {
    public function __construct($one, &$two, &$three) {
        $this->one=$one;
        $this->two=$two;
        $this->three=$three;
        echo "[New:\$one={$one}]:";
    }
    //public function &get($what){
    public function &get($what){
        //echo "<p>You asked for $what. $what ain't no country I ever heard of.<br />";
        echo "Get:{$what}:[{$this->one}]<br />";
        if(!isset($this->obj[$what])){
            $this->obj[$what] = new testcaseB(++$this->one,$this->two,$this->three);
        }
        return $this->obj[$what];
    } 
}
echo "STARTING:<br />";
ini_set('display_errors',1); 
error_reporting(E_ALL);
echo "REALLY STARTING:<br />";
echo "<pre>";
echo "<p>One at a time:</p>";
$bob = new testcaseA();
$a=$bob->get("What");
$b=$a->get("Spam");
$c=$b->get("America");
$d=$a->get("EU");
$e=$d->get("France"); 
echo "<br />";
print_r($bob); 
echo "<p>Chained:</p>";
$bobby = new testcaseA();
$bobby->get("What")->get("Spam")->get("America");
$bobby->get("What")->get("EU")->get("France");
echo "<br />";
print_r($bob);

输出结果是：

输出数字似乎正确，但$one在堆栈中关闭。

Answer 1

如果我理解你对此感到困惑（并且我认为我做了），你会遇到pre- and post-increment之间的细微差别。这可以在代码中最容易地证明：

$a = 1;
echo $a++; // 1
echo $a;   // 2

另一方面：

$a = 1;
echo ++$a; // 2
echo $a;   // 2

基本上，通过在之前放置++ 您增加的值，您将获得新值。通过将其放置（如您所做），您将获得旧值。

我认为代码中的关键字是：

$this->obj[$what] = new testcaseB($this->one++,$this->two,$this->three);

......应该是这样的：

$this->obj[$what] = new testcaseB(++$this->one,$this->two,$this->three);

通过后增量，$this->one的初始值将在所有后续迭代中进行。

作为旁注，我认为你不必担心在这里通过引用返回，因为PHP5中的所有对象都是通过引用传递的。

PHP 5：通过ref方法返回产生意外结果

1 个答案: