arrays - PHP array_merge with numerical keys

Question

How can make it so array_merge() overwrites two keys with different values but same key index from two arrays?

for example, merging:

[0] => 'whatever'

with

[0] => 'whatever', [1] => 'a', [2] => 'b'

should produce

[0] => 'whatever', [1] => 'a', [2] => 'b'

Basically I want array_merge to bahave the same way it behaves if the arrays have string keys...

Answer 1

Use the + operator.

Compare array_merge to + operator:

<?php

$a1 = array(0=>"whatever",);
$a2 = array(0=>"whatever",1=>"a",2=>"b");

print_r(array_merge($a1,$a2));
print_r($a1+$a2);
?>

Output:

Array
(
    [0] => whatever
    [1] => whatever
    [2] => a
    [3] => b
)
Array
(
    [0] => whatever
    [1] => a
    [2] => b
)

The + operator still works if your associative array has the numerical keys out-of-order:

<?php

$a1 = array(0=>"whatever",);
$a2 = array(1=>"a",0=>"whatever",2=>"b");

print_r(array_merge($a1,$a2));
print_r($a1+$a2);
?>

Output:

Array
(
    [0] => whatever
    [1] => a
    [2] => whatever
    [3] => b
)
Array
(
    [0] => whatever
    [1] => a
    [2] => b
)

Notice array_merge in this case creates a new key. Not desirable...