Overwrite associative elements of one array with another associative array and reverse the array order

This is the First Array:

Array
(
    [6] => 1
    [8] => 1
    [9] => 5
)

Second Array:

Array
(
    [9] => 0
    [8] => 0
    [7] => 0
    [6] => 0
    [5] => 0
    [4] => 0
    [3] => 0
    [2] => 0
    [1] => 0
    [12] => 0
    [11] => 0
    [10] => 0
)

Desired Output Array:

Array
(
    [10] => 0
    [11] => 0
    [12] => 0
    [1] => 0
    [2] => 0
    [3] => 0
    [4] => 0
    [5] => 0
    [6] => 1
    [7] => 0
    [8] => 1
    [9] => 5
)

Simply I want to array to sort reverse but with the first array value. I have tried array_reverse but it only short the array in reverse and misplace the value of it.

Note: the desired array key is the previous 12 month

I have looked the suggested sort array technique but it didn't help

Check working demo here: https://eval.in/856000

<?php 
$array1 = array(6 => 1,
    8 => 1,
    9 => 5);

$array2 = array(9 => 0,
    8 => 0,
    7 => 0,
    6 => 0,
    5 => 0,
    4 => 0,
    3 => 0,
    2 => 0,
    1 => 0,
    12 => 0,
    11 => 0,
    10 => 0);
$mergedArray =[];

foreach ($array2 as $key => $value) {

    if (array_key_exists($key, $array1)) {      
        if ($array1[$key] > $array2[$key]) {
          $mergedArray[$key] = $array1[$key];
        }
        else {
          $mergedArray[$key] = $array2[$key];
        }
    }
    else {
        $mergedArray[$key] = $array2[$key];
    }
}

print_r(array_reverse($mergedArray,true));

 ?>

Output:

Array
(
    [10] => 0
    [11] => 0
    [12] => 0
    [1] => 0
    [2] => 0
    [3] => 0
    [4] => 0
    [5] => 0
    [6] => 1
    [7] => 0
    [8] => 1
    [9] => 5
)