mysql fetch_array에러 채택완료

          $sql = mq("SELECT * FROM board order by idx desc limit 0,2");           echo $sql;             while($board = fetch_array($sql))             {

              $title=$board["title"];               if(strlen($title)>30)               {

                $title=str_replace($board["title"],mb_substr($board["title"],0,30,"utf-8")."...",$board["title"]);               }

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#dbc.php

    $db = new mysqli("localhost","","","");     $db->set_charset("utf8");

    function mq($sql)     {         global $db;         return $db->query($sql);     } ?>  

이렇게 돌리면 

Fatal error: Uncaught Error: Call to undefined function fetch_array() in C:\xampp\htdocs\bimain.php:30 Stack trace: #0 {main} thrown in C:\xampp\htdocs\bimain.php on line 30

라고 오류가 뜨는데 한번 봐주실수있을까요.. ㅜㅜ