php “间接修改 SplFixedArray 的重载元素无效”
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"Indirect modification of overloaded element of SplFixedArray has no effect"
提问by Desmond Hume
Why the following
为什么以下
$a = new SplFixedArray(5);
$a[0] = array(1, 2, 3);
$a[0][0] = 12345; // here
var_dump($a);
produces
产生
Notice: Indirect modification of overloaded element of SplFixedArray has no effect in <file> on line <indicated>
Is it a bug? How do you deal with multidimensional SplFixedArrays then? Any workarounds?
这是一个错误吗？那么你如何处理多维 SplFixedArrays 呢？任何解决方法？
回答by hek2mgl
First, the problem is related to all classes which implement ArrayAccessit is not a special problem of SplFixedArrayonly.
首先，该问题与实现ArrayAccess它的所有类有关，而不仅仅是一个特殊问题SplFixedArray。
When you accessing elements from SplFixedArrayusing the []operator it behaves not exactly like an array. Internally it's offsetGet()method is called, and will return in your case an array - but not a referenceto that array. This means all modifications you make on $a[0]will get lost unless you save it back:
当您SplFixedArray使用[]运算符访问元素时，它的行为与数组不完全相同。在内部offsetGet()调用它的方法，并在您的情况下返回一个数组 -但不是对该数组的引用。这意味着您所做的所有修改都$a[0]将丢失，除非您将其保存回来：
Workaround:
解决方法：
$a = new SplFixedArray(5);
$a[0] = array(1, 2, 3);
// get element
$element = $a[0];
// modify it
$element[0] = 12345;
// store the element again
$a[0] = $element;
var_dump($a);
Here is an example using a scalarwhich fails too - just to show you that it is not related to array elements only.
回答by mpen
This is actually fixable if you slap a &in front of offsetGet(assuming you have access to the internals of your ArrayAccessimplementation):
这实际上是可以修复的，如果你&在前面打一个耳光offsetGet（假设你可以访问你的ArrayAccess实现的内部）：
class Dict implements IDict {
private $_data = [];
/**
* @param mixed $offset
* @return bool
*/
public function offsetExists($offset) {
return array_key_exists(self::hash($offset), $this->_data);
}
/**
* @param mixed $offset
* @return mixed
*/
public function &offsetGet($offset) {
return $this->_data[self::hash($offset)];
}
/**
* @param mixed $var
* @return string
*/
private static function hash($var) {
return is_object($var) ? spl_object_hash($var) : json_encode($var,JSON_UNESCAPED_SLASHES);
}
/**
* @param mixed $offset
* @param mixed $value
*/
public function offsetSet($offset, $value) {
$this->_data[self::hash($offset)] = $value;
}
/**
* @param mixed $offset
*/
public function offsetUnset($offset) {
unset($this->_data[self::hash($offset)]);
}
}
回答by mils
Adding my experience with the same error, in case it helps anyone:
添加我对相同错误的经验，以防它对任何人有帮助：
I recently imported my code into a framework with a low error-tolerance (Laravel). As a result, my code now throws an exception when I try to retrieve a value from an associative array using a non-existent key. In order to deal with this I tried to implement my own dictionary using the ArrayAccess interface. This works fine, but the following syntax fails:
我最近将我的代码导入到一个低容错框架 (Laravel) 中。因此，当我尝试使用不存在的键从关联数组中检索值时，我的代码现在会引发异常。为了解决这个问题，我尝试使用 ArrayAccess 接口实现我自己的字典。这工作正常，但以下语法失败：
$myDict = new Dictionary();
$myDict[] = 123;
$myDict[] = 456;
And in the case of a multimap:
在多图的情况下：
$properties = new Dictionary();
$properties['colours'] = new Dictionary();
$properties['colours'][] = 'red';
$properties['colours'][] = 'blue';
I managed to fix the problem with the following implementation:
我设法通过以下实现解决了这个问题：
<?php
use ArrayAccess;
/**
* Class Dictionary
*
* DOES NOT THROW EXCEPTIONS, RETURNS NULL IF KEY IS EMPTY
*
* @package fnxProdCrawler
*/
class Dictionary implements ArrayAccess
{
// FOR MORE INFO SEE: http://alanstorm.com/php_array_access
protected $dict;
function __construct()
{
$this->dict = [];
}
// INTERFACE IMPLEMENTATION - ArrayAccess
public function offsetExists($key)
{
return array_key_exists($key, $this->dict);
}
public function offsetGet($key)
{
if ($this->offsetExists($key))
return $this->dict[$key];
else
return null;
}
public function offsetSet($key, $value)
{
// NOTE: THIS IS THE FIX FOR THE ISSUE "Indirect modification of overloaded element of SplFixedArray has no effect"
// NOTE: WHEN APPENDING AN ARRAY (E.G. myArr[] = 5) THE KEY IS NULL, SO WE TEST FOR THIS CONDITION BELOW, AND VOILA
if (is_null($key))
{
$this->dict[] = $value;
}
else
{
$this->dict[$key] = $value;
}
}
public function offsetUnset($key)
{
unset($this->dict[$key]);
}
}
Hope it helps.
希望能帮助到你。
回答by Leopoldo Sanczyk
I did a workaround to this problem extending SplFixedArrayand overriding offsetGet()to return a reference*
But as this hek2mglmentioned, it could lead to side effects.
我对这个问题进行了解决方法扩展SplFixedArray和覆盖offsetGet()以返回引用* 但是正如这个hek2mgl提到的那样，它可能会导致副作用。
I shared the code to do it, because I couldn't find it in other place. Note is not serious implementation, because I'm not even checking the offset exists (I will be glad if someone propose enhancements), but it works:
我分享了代码来做到这一点，因为我在其他地方找不到它。注意不是认真的实现，因为我什至没有检查偏移量是否存在（如果有人提出改进，我会很高兴），但它有效：
class mySplFixedArray extends SplFixedArray{
public function &offsetGet($offset) {
return $this->array[$offset];
}
}
I was changing native PHP hash like arrays for these less memory consuming fixed length arrays, and some of the other things I have to change too (either as a consequence of the lazy extending of the class SplFixedArray, or just for not using native arrays) were:
我正在为这些较少内存消耗的固定长度数组更改原生 PHP 散列，如数组，还有一些我必须更改的其他内容（要么是 SplFixedArray 类的延迟扩展的结果，要么只是因为不使用原生数组）是：
- Creating a manual method for copying my class objects property by property.
clonedidn't worked anymore. - Use
a[i]!==NULLto check if the element exists, becauseisset()didn't worked anymore. - Add an
offsetSet()method to the extended class too:public function offsetSet($offset,$value) { $this->array[$offset]=$value; }
- 创建一个按属性复制我的类对象属性的手动方法。
clone没有工作了。 - 使用
a[i]!==NULL来检查元素存在，因为isset()没有了工作。 - 也
offsetSet()向扩展类添加一个方法：public function offsetSet($offset,$value) { $this->array[$offset]=$value; }
(*) I think this overriding is only possible after some PHP version between 5.2.6 and 5.3.4. I couldn't find too much info or code about this problem, but I want to share the solution for other people anyway.
(*) 我认为这种覆盖只有在 5.2.6 和 5.3.4 之间的某些 PHP 版本之后才有可能。我找不到关于这个问题的太多信息或代码，但无论如何我想为其他人分享解决方案。
回答by Tom
I guess SplFixedArray is incomplete/buggy.
我猜 SplFixedArray 不完整/有问题。
If i wrote an own class and it works like a charm:
如果我写了一个自己的类，它就像一个魅力：
$a = new \myArrayClass();
$a[0] = array(1, 2, 3);
$a[0][0] = 12345;
var_dump($a->toArray());
Output (no notices/warnings here, in strict mode too):
输出（这里没有通知/警告，在严格模式下也是如此）：
array (size=1)
0 =>
array (size=3)
0 => int 12345
1 => int 2
2 => int 3
Using the [] operator is not a problem (for assoc/mixed arrays too). A right implementation of offsetSet should do the job:
使用 [] 运算符不是问题（对于关联/混合数组也是如此）。offsetSet 的正确实现应该可以完成这项工作：
public function offsetSet($offset, $value) {
if ($offset === null) {
$offset = 0;
if (\count($this->array)) {
$keys = \preg_grep( '#^(0|([1-9][0-9]*))$#', \array_keys($this->array));
if (\count($keys)) {
$offset = \max($keys) + 1;
}
}
}
...
But there is only one exception. Its not possible to use the [] operator for offset which does not exist. In our example:
但只有一种例外。无法将 [] 运算符用于不存在的偏移量。在我们的例子中：
$a[1][] ='value'; // Notice: Indirect modification of overloaded...
It would throw the warning above because ArrayAccess calls offsetGet and not offsetSet for [1] and the later [] fails. Maybe there is a solution out there, but i did not find it yet. But the following is working without probs:
它会抛出上面的警告，因为 ArrayAccess 为 [1] 调用 offsetGet 而不是 offsetSet 并且后面的 [] 失败。也许那里有解决方案，但我还没有找到。但以下工作没有问题：
$a[] ='value';
$a[0][] ='value';
I would write an own implementation instead of using SplFixedArray. Maybe its possible to overload some methods in SplFixedArray to fix it, but i am not sure because i never used and checked SplFixedArray.
我会编写自己的实现而不是使用 SplFixedArray。也许可以重载 SplFixedArray 中的某些方法来修复它，但我不确定，因为我从未使用和检查过 SplFixedArray。
