PHP查詢數據庫里數據，用表格形式輸出頁面

<?php
$conn = mysqli_connect('localhost', 'root', '密碼');
if(! $conn )
{
die('Could not connect: ' . mysqli_error());
}
//echo '數據庫連接成功！';

// 設置編碼，防止中文亂碼
mysqli_query($conn , "set names utf8");

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

mysqli_select_db($conn,'test');
$retval = mysqli_query( $conn, $sql );
if(! $retval )
{
die('無法讀取數據: ' . mysqli_error($conn));
}

echo '<table border="1"><tr><td>ID</td><td>IMEI號</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);
?>