php - Array_merge 与 +

Question

这个问题在这里已经有了答案:

What's the difference between array_merge and array + array? [duplicate] (9 个回答)

关闭 6年前。

当我将 array_merge() 与关联数组一起使用时，我得到了我想要的，但是当我将它们与数字键数组一起使用时，键会改变。

使用 + 会保留键，但它不适用于关联数组。

我不明白这是怎么回事，谁能给我解释一下？

Answer 1

因为两个数组都是数字索引的，所以只会使用第一个数组中的值。

The + operator returns the right-hand array appended to the left-hand array; for keys that exist in both arrays, the elements from the left-hand array will be used, and the matching elements from the right-hand array will be ignored.

http://php.net/manual/en/language.operators.array.php

array_merge() 的行为略有不同:

If the input arrays have the same string keys, then the later value for that key will overwrite the previous one. If, however, the arrays contain numeric keys, the later value will not overwrite the original value, but will be appended. Values in the input array with numeric keys will be renumbered with incrementing keys starting from zero in the result array.

http://php.net/manual/en/function.array-merge.php