PHP怎么将查询结束导出Excel

<form action="user.php" method="POST"><br />
	用户编号：<input type="text" name="u_num" size="12" value="<?php echo $_POST['u_num']; ?>" />  <br />
	用户名：<input type="text" name="u_name" size="20" value="<?php echo $_POST['u_name']; ?>" />  <br />
	<input type="submit" name="sub" value=" 查询 " />      <br />
	<input type="button" value="导出Excel" /><br />
</form><br />
<br />
<table><br />
	<tr><br />
		<td>用户编号</td><br />
		<td>用户名</td><br />
	</tr><br />
<br />
<?php	<br />
if(!empty($_POST["u_num"])){<br />
	$u_num = "where u_id='"."{$_POST['u_num']}"."'";<br />
}<br />
<br />
$sql = "select * from msd.dbo.user";<br />
<br />
$query = sqlsrv_query($conn,$sql);<br />
if( $query === false) {<br />
    die( print_r( sqlsrv_errors(), true) );<br />
}<br />
<br />
while($row = sqlsrv_fetch_array($query)) {<br />
	echo "<tr><td>$row[0]</td><td>$row[1]</td></tr>";<br />
}<br />
<br />
sqlsrv_free_stmt( $query);<br />
sqlsrv_close( $conn);<br />
?><br />
<br />
</table>