subset_sum([11.96,1,15.04,7.8,20,10,11.13,9,11,1.07,8.04,9], 20);


function subset_sum($a,$s,$c = array())
{
        if($s<0)
                return;
        if($s!=0&&count($a)==0)
                return;
        if($s!=0)
        {
                foreach($a as $xd=>$xdd)
                {
                        unset($a[$xd]);
                        subset_sum($a,$s-$xdd,array_merge($c,array($xdd)));
                }
        }
        else
                print_r($c);

}