“间接修改 SplFixedArray 的重载元素没有效果" [英] "Indirect modification of overloaded element of SplFixedArray has no effect"

问题描述

为什么会出现以下情况

$a = new SplFixedArray(5);$a[0] = 数组(1, 2, 3);$a[0][0] = 12345;//这里var_dump($a);

生产

注意:间接修改SplFixedArray的重载元素对没有影响.在线<指示>

这是一个错误吗?那么你如何处理多维 SplFixedArrays 呢?有什么解决方法吗?

解决方案

首先，问题与所有实现ArrayAccess的类有关，不是SplFixedArray的特殊问题> 仅.

<小时>

当您使用 [] 运算符从 SplFixedArray 访问元素时，它的行为与数组不完全相同.在内部调用 offsetGet() 方法，并且在您的情况下将返回一个数组 - 但不是对该数组的引用.这意味着您对 $a[0] 所做的所有修改都将丢失，除非您将其保存回来:

解决方法:

$a = new SplFixedArray(5);$a[0] = 数组(1, 2, 3);//获取元素$element = $a[0];//修改它$元素[0] = 12345；//再次存储元素$a[0] = $element;var_dump($a);

这是一个使用标量的示例，它也失败了 - 只是为了向您展示它不仅仅与数组元素相关.>

Why the following

$a = new SplFixedArray(5);
$a[0] = array(1, 2, 3);
$a[0][0] = 12345; // here
var_dump($a);

produces

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?

解决方案

First, the problem is related to all classes which implement ArrayAccess it is not a special problem of SplFixedArray only.

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When you accessing elements from SplFixedArray using 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 reference to that array. This means all modifications you make on $a[0] will get lost unless you save it back:

Workaround:

$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 scalar which fails too - just to show you that it is not related to array elements only.

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