使用+运算符组合PHP中的数组

Question

我最近发现，+可以用于组合PHP中的数组。

将关联数组添加到关联数组：

$array1 = ["The" => "quick", "brown" => "fox"];
$array2 = ["jumps" => "over", "the" => "lazy dog"];

$combinedArray = $array1 + $array2;

/* Gives:

Array
(
    [The] => quick
    [brown] => fox
    [jumps] => over
    [the] => lazy dog
)

*/

将关联数组添加到索引数组：

$array1 = ["The", "quick", "brown", "fox"];
$array2 = ["jumps" => "over", "the" => "lazy dog"];

$combinedArray = $array1 + $array2;

/* Gives:

Array
(
    [0] => The
    [1] => quick
    [2] => brown
    [3] => fox
    [jumps] => over
    [the] => lazy dog
)

*/

将索引数组添加到关联数组：

$array1 = ["The" => "quick", "brown" => "fox"];
$array2 = ["jumps", "over", "the", "lazy dog"];

$combinedArray = $array1 + $array2;

/* Gives:

Array
(
    [The] => quick
    [brown] => fox
    [0] => jumps
    [1] => over
    [2] => the
    [3] => lazy dog
)

*/

将索引数组添加到索引数组：

$array1 = ["The", "quick", "brown", "fox"];
$array2 = ["jumps", "over", "the", "lazy dog"];

$combinedArray = $array1 + $array2;

/* Gives:

Array
(
    [0] => The
    [1] => quick
    [2] => brown
    [3] => fox
)

*/

其中一个和其他的不一样。

为什么最后一个不能用？

Answer 1

这是因为上一个示例中的两个数组具有相同的键：

+操作符返回附加到左侧数组的右数组；对于两个数组中存在的键，将使用来自左侧数组的元素，而忽略来自右侧数组的匹配元素。

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