PHP Merge arrays + array_merge differences _php Tutorial

The combination of two arrays in PHP can use + or array_merge, but these two are still different, it is clear to understand the difference between the two approaches to the rapid development of the project is still very necessary.

The main difference is that when the same key name appears in two or more arrays, you need to be aware of the following two points:

First of all, it is necessary to explain that the array key names in PHP can be divided into strings (associative arrays) or numbers (numeric arrays), and this does not discuss multidimensional arrays.

(1) When the key name is a number (numeric array), Array_merge () does not overwrite the original value, but the + merge array will return the first occurrence as the final result, and the values of the following array with the same key name "Discard" (not overwrite).

(2) When the key name is a character (associative array), + still returns the first occurrence as the final result, and "discards" the values of the following array with the same key name, but Array_merge () overwrites the previous value of the same key name.

This is illustrated by a few specific examples:

M:array (
[0] = a
[1] = b
)
N:array (
[0] = C
[1] = d
)
The m+n result is: Array (
[0] = a
[1] = b
)
The Array_merge (m,n) result is: Array (
[0] = a
[1] = b
[2] = C
[3] = d
)
M:array (
[1] = a
[2] = b
)
N:array (
[2] = C
[3] = d
)
The m+n result is: Array (
[1] = a
[2] = b
[3] = d
)
The Array_merge (m,n) result is: Array (
[0] = a
[1] = b
[2] = C
[3] = d
)
M:array (
[A] = a
[B] = b
)
N:array (
[b] + = C
[d] + D
)
The m+n result is: Array (
[A] = a
[B] = b
[d] + D
)
The Array_merge (m,n) result is: Array (
[A] = a
[b] + = C
[d] + D
)

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