How to merge two arrays and sum the values of duplicate keys?

I would like to merge array by conditions. If array keys match then add the values, if not then retain the value.

Here are my arrays:

Array1
(   
    [1] => 199
    [3] => 1306
    [5] => 199
)

Array2
(  
   [3] => 199
   [4] => 199
)

My desired result is:

Result
(  
   [1] => 199
   [3] => 1505
   [4] => 199
   [5] => 199    
)

I used if-else conditions, but it's repeating the value which is already matched.

Here is my coding attempt:

$all=array();   
foreach($sall as $sskey => $ssvalue){
    foreach($upgradesall as $uukey => $uuvalue){
        //$sskey==$uukey?$all[] = array("id"=>$sskey, "amount"=>$ssvalue+$uuvalue):($sskey!=$uukey? $all[] = array("id"=>$sskey, "amount"=>$ssvalue):($uukey!=$sskey?$all[] = array("id"=>$uukey, "amount"=>$uuvalue):''));
        if($sskey===$uukey){
            $all[] = array("id"=>$sskey, "amount"=>$ssvalue+$uuvalue);
        }elseif($sskey!=$uukey){
            $all[] = array("id"=>$sskey, "amount"=>$ssvalue);
        }elseif($uukey!=$sskey){
            $all[] = array("id"=>$uukey, "amount"=>$uuvalue);
        }
    }
}