mysqli fetch数组总是不返回任何内容

Question

My code is returning nothing. I can't understand what the problem is.

my code

$results = $mysqli->query("SELECT * FROM tbl_pdf ORDER BY id DESC");

    $dataarray = array();
    while($row =mysqli_fetch_array($results))
    {

        $dataarray [] = [
            'id'=>$row['id'],
            'ptitle'=>$row['ptitle'],
            'pdate'=>$row['pdate'],
            'filelink'=>'http://'.$_SERVER['SERVER_NAME'].'/'.$row['filelink'],
            'status'=>$row['status']
        ];

    }

    echo json_encode($dataarray);