php成绩排序

$arr = ['12','12','23'];
$arr = $arr;
        $arr1=$arr;
        rsort($arr1);
        $c=[];
        foreach ( $arr as $k=>$v){
            $b= array_search($v, $arr1);
            $c[$k]=$b+1;
        }

//另一种方法

public function rsort(){
        $str='100,99,98,99,97,96,99,36,98,100';

        $array=[];

        $array = explode(',', $str);

        explode(',', $str);

        //array_pop($array);

        $new_array=[];

        rsort($array);
       // dump($array);$paiming='';

        foreach ($array as $key => $value) {
            # code...
            $num=Session::get('num');
            $keys=Session::get('keys');

            if($array[$key]==$num){
                $paiming .= $keys;

            }else{
               $paiming .= $key+1;
               Session::set('keys',$key+1);
            }

            Session::set('num',$array[$key]);
            //dump($paiming);
        }

       // dump($paiming);
    }