尝试按降序对值进行排序和存储.我做不到

public function gl_popular(){
$query=$this->db->query("SELECT DISTINCT new_ques_id FROM gl_mark_ques");
//echo "SELECT DISTINCT new_ques_id FROM gl_mark_ques" ."<br>";
if($query->num_rows > 0){
$question = array();
        foreach($query->result() as $row){
        $question[]=array(
        'question'=>$row->new_ques_id,
        'quest'=> $this->gl_avg_pop($row->new_ques_id),//tryin to sort according to this.
        'get_quest'=>$this->gl_get_question($row->new_ques_id),
        );
        }
        $av=array();
        //$av=asort($question[1]);
        rsort($question[1]);
        foreach ($question as $key => $val) {
        echo "$key = $val'n";
        }
        //return $question;
        //var_dump($av);
        }
}

问题是$question['quest']给了我一个浮点数。我需要以这样一种方式存储数组，最高的浮点数将放在第一位。就是做不到。请帮助。