Mengatasi error mysql

Jadi ceritanya saya lagi mau coba buat fitur print pdf, tapi begitu mulai munculin data error

Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given in ... on line 34

itu warningnya, padahal webnya lancar jaya sentosa

<?php
include '../lib/db/dbconfig.php';
$sql = mysqli_select_db($conn,"SELECT*FROM detail_user u inner join data_absen a on u.id_user=a.id_user");
$result=mysql_query($sql);

$content = '
<style type= "text/css">
.tabel { border-collapse:collapse; }
.tabel th { padding:8px 5px; background-color:#ADFF2F; }
</style>
';

$content .='
<page>

	<div>
	<h2> Laporan Absensi</h2>
	</div>

	<div style="padding:20px 0 10px; font-size:15px;">
	Bimbingan Teknis
	</div>

	<table border="1px" class="tabel">
		<tr>
			<th>No.</th>
			<th>Nama Peserta</th>
			<th>Asal Instansi</th>
			<th>Jam Absen</th>
			<th>Status</th>
		</tr>';
		$no=0;
		while($d = mysqli_fetch_array($result)){
			 		$content .= '
			 		<tr>
			                <td align="center">'.$no++.'</td>
			                <td>'.$d->name_user.'</td>
			                <td>'.$d->sklh_user.'</td>
			                <td>'.$d->jam_msk.'</td>
			                <td>'.$d->st_jam_msk.'</td>
			              </tr>';
			          }


$content .= '

	</table>

</page>';

require_once('../lib/html2pdf/html2pdf.class.php');
$html2pdf = new HTML2PDF('P','A4','en');
$html2pdf->WriteHTML($content);
$html2pdf->Output('report.pdf');
?>

Minta bantuan solusinya ya,