function mergeArrays($arr1, $arr2) {
$mergedArray = [];
$i = $j = 0;
while ($i < count($arr1) && $j < count($arr2)) {
if ($arr1[$i] < $arr2[$j]) {
$mergedArray[] = $arr1[$i];
$i++;
} else {
$mergedArray[] = $arr2[$j];
$j++;
}
}
// Add remaining elements
while ($i < count($arr1)) {
$mergedArray[] = $arr1[$i];
$i++;
}
while ($j < count($arr2)) {
$mergedArray[] = $arr2[$j];
$j++;
}
return $mergedArray;
}
$arr1 = [1, 3, 5, 7, 8, 9, 9];
$arr2 = [2, 3, 4, 5, 6, 9];
print_r(mergeArrays($arr1, $arr2));
/*
run:
Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 3
[4] => 4
[5] => 5
[6] => 5
[7] => 6
[8] => 7
[9] => 8
[10] => 9
[11] => 9
[12] => 9
)
*/