PHP merges arrays + and array_merge

You can use + or array_merge to merge two arrays in PHP, but there are still differences between the two. It is necessary to clearly understand the differences in the two Processing Methods for rapid development of the project.
 
The main difference is that if the same key name appears in two or more arrays, pay attention to the following two points:

First, you must note that the array key names in php can be divided into strings (associated arrays) or numbers (numeric arrays). Here we will not discuss multi-dimensional arrays.
 
(1) When the key name is a number (value array), array_merge () does not overwrite the original value, but + merges the array to return the first value as the final result, the values of the following arrays with the same key names are discarded (not overwritten ).
 
(2) When the key name is a character (associated array), + returns the first value as the final result, and discards the values with the same key name in the subsequent array, however, array_merge () overwrites the values with the same key name.

The following are examples:

M: Array (
[0] =>
[1] => B
)
N: Array (
[0] => c
[1] => d
)
M + n: Array (
[0] =>
[1] => B
)
The result of array_merge (m, n) is: Array (
[0] =>
[1] => B
[2] => c
[3] => d
)
M: Array (
[1] =>
[2] => B
)
N: Array (
[2] => c
[3] => d
)
M + n: Array (
[1] =>
[2] => B
[3] => d
)
The result of array_merge (m, n) is: Array (
[0] =>
[1] => B
[2] => c
[3] => d
)
M: Array (
[A] =>
[B] => B
)
N: Array (
[B] => c
[D] => d
)
M + n: Array (
[A] =>
[B] => B
[D] => d
)
The result of array_merge (m, n) is: Array (
[A] =>
[B] => c
[D] => d
)

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