PHP查询数据库里数据，用表格形式输出页面

<?php
$conn = mysqli_connect('localhost', 'root', '密码');
if(! $conn )
{
die('Could not connect: ' . mysqli_error());
}
//echo '数据库连接成功！';

// 设置编码，防止中文乱码
mysqli_query($conn , "set names utf8");

$sql = 'SELECT id, IMEI FROM db_imei';

mysqli_select_db($conn,'test');
$retval = mysqli_query( $conn, $sql );
if(! $retval )
{
die('无法读取数据: ' . mysqli_error($conn));
}

echo '<table border="1"><tr><td>ID</td><td>IMEI号</td></tr>';
while($row = mysqli_fetch_array($retval, MYSQLI_ASSOC))
{
echo "<tr><td> {$row['id']}</td> "."<td>{$row['IMEI']} </td> "."</tr>";
}
echo '</table>';
mysqli_close($conn);
?>