Get highest value from multidimensional array

Here is my multidimensional array:

$arrOrg = [2, 3, [5, 7, 1], 100, [6, 9, [14, 95]], 78];

I want to get the highest value from this array.

Here is what I have tried so far:

$highest = 0;
function getHighest($arr) {
    for ($i = 0; $i < count($arr); $i++) {
        if (is_array($arr[$i])) {
            getHighest($arr[$i]);
        } else {
            if ($arr[$i] > $arr[$i + 1]) {
                $highest = $arr[$i];
            } else {
                $highest = $arr[$i + 1];
            }
        }
    }
    return $highest;
}
echo getHighest($arrOrg);

But it is giving an incorrect result: 78

Can you help me out?