如何在php中将一个数组追加到另一个数组

Question

I have to arrays in script

    $users = array("A", "B", "C", "D", "E");
    $newUsers = array("F", "G", "H", "I");
    $totalUsers = $users + $newUsers;

By using Union operator, I tried to append $newUser array to $users .

And store it in $totalUsers , after printing the $totalUsers by using print_r($totalUsers) .

It printed out only the $users array contents. Why ?

I used the array_merge($users + $newUsers) and also it printed only the $users array contents.

Finally by using one of the following methods,

method 1:

    $totalUsers = array_merge(array_values($users), array_values($newUsers));
    print_r($totalUsers);

method 2:

    array_merge($users, $newUsers);
    print_r($totalUsers);

I got the correct output

(
    [0] => A
    [1] => B
    [2] => C
    [3] => D
    [4] => E
    [5] => F
    [6] => G
    [7] => H
    [8] => I
)

What was the problem, and what is different between the above methods??

Answer 1

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

In other words, it only adds elements from the right hand if the keys don't already exist in the left hand array. That explains why it does nothing in your case.

array_merge($users + $newUsers)

This does exactly the same, an array union, and afterwards does an array_merge on the result. So it does nothing either.

array_merge($users, $newUsers)

This does exactly what you want, it's the correct thing to do.

array_merge(array_values($users), array_values($newUsers))

This does the exact same thing as well, array_values does nothing in this case.

Answer 2

$totalUsers = array_merge($users, $newUsers);

That is the correct way to use array_merge . You can also input more then two arrays to be merged.

EDIT: To read more on the array operators, please visit this link: http://php.net/manual/en/language.operators.array.php