mysql fetch_array에러

<?php
  include ('dbc.php');
  $board_id = $_GET['id'];

          $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"]);
              }

--------------------------------------------------

#dbc.php

<?php
    session_start();
    header('Content-Type: text/html; charset=utf-8');

    $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