Array_merge_recursive gives me repeat data, how to remove it - php

Question

I have the following 2 arrays that I'm trying to merge recursively so that I don't lose data, but I also don't want any data repeated.
$a = array(
'group1' => array(
'names' => array(
'g1name1',
'g1name2'
)
),
'group2' => array(
'names' => array(
'g2name1'
)
)
);
$b = array(
'group1' => array(
'names' => array(
'g1name1',
'g1name3'
),
'extras' => array(
'g1extra1'
)
),
'group3' => array(
'names' => array(
'g3name1'
)
)
);
I'm using array_merge_recursive($a, $b); which works fine for group2 and group3 because they exist in either $a or $b, but group1 is giving me a problem because it has some duplicate data in both $a and $b. This is what I'm getting after I merge recursively. Notice that in names, g1name is listed twice, once from $a and once from $b.
'group1' =>
array
'names' =>
array
0 => string 'g1name1'
1 => string 'g1name2'
2 => string 'g1name1'
3 => string 'g1name3'
'extras' =>
array
0 => string 'g1extra1'
1 => string 'g1extra2'
'group2' => ....
'group3' => ....
I tried array_unique like this array_unique(array_merge_recursive($a, $b)) but it's giving me strange results (doesn't fix the repeat problem and deletes group2 and group3 entirely).

Answer 1

Use array_replace_recursive instead of array_merge_recursive.

Answer 2

The the following should work for you:
array_walk($arr, function(&$data, $key) {
foreach ($data as &$arr) {
$arr = array_values(array_unique($arr));
}
});
Result:
Array
(
[group1] => Array
(
[names] => Array
(
[0] => g1name1
[1] => g1name2
[2] => g1name3
)
[extras] => Array
(
[0] => g1extra1
)
)
[group2] => Array
(
[names] => Array
(
[0] => g2name1
)
)
[group3] => Array
(
[names] => Array
(
[0] => g3name1
)
)
)

Answer 3

Sadly, array_replace_recursive (PHP 5.3.0)­Docs does not work (Demo).
Luckily Tim Cooper pointed that out and made some suggestion. I was not very creative with my new suggestion, so it's highly influenced by his solution:
$result = array_merge_recursive($a, $b);
array_walk($result, function(&$v) {
$v = array_map('array_unique', $v);
});
New Demo