bagaimana kl begini?

$array= Array
(
    "RT III" => 3,
    "RT II" => 2,
    "RT I" => 2,
    "RT V" => 1,
    "RT IV" => 1,
    "RT IX" => 4,
    "RT X" => 4,
    "RT XI" => 5,
);



foreach($array as $key=>$val){
        $data2[$val][] = $key;

}
krsort($data2);


    foreach($data2 as $ar2){
    $ar3=array();
    foreach($ar2 as $i=>$v){
            if($i>=2) {
              echo implode(', ',$ar3),"<br />";unset($data2);
          break;
            }
    $ar3[]=$v;
    }
    echo implode(', ',$ar3),"<br />";
    }

/*
hasilnya masih :
RT XI
RT IX, RT X
RT III
RT II, RT I
RT V, RT IV

inginya cuma :
RT XI
RT IX, RT X
*/