mysqli 的多sql语句执行有关问题

mysqli 的多sql语句执行问题

<?php<br />	//对象创建<br />	$mysqli = new mysqli('localhost', 'root', 'nagiosxi'，'hrsystem');<br />	//连接是否出错<br />	if($mysqli->connect_error)<br />	{<br />		die('connect database error'.mysqli_connect_error());<br />	}<br />	$sql = "insert into login (user, pass, email, type) values ('dengchao1', md5('dengchao123'), [email&#160;protected]', 0);";<br />	$sql .= "insert into login (user1, pass, email, type) values ('dengchao1', md5('dengchao123'), [email&#160;protected]', 0)";<br />	$res = $mysqli->multi_query($sql);<br />	if($res && $mysqli->affected_rows > 0)<br />	{<br />		echo "insert ok <br />rows: ".$mysqli->affected_rows;<br />	}<br />	else<br />	{<br />		//$mysqli->close();<br />		die('insert error <br />'.$mysqli->error.$mysqli->close());<br />	}<br />	if(!is_bool($res))<br />	{<br />		$res->free();<br />	}<br /><br />	$sql = "select * from login";<br />	$res = $mysqli->query($sql);<br />        echo $mysqli->error."<br />";<br />	if($res)<br />	{<br />		while($row = $res->fetch_row())<br />		{<br />			foreach($row as $key => $val)<br />			{<br />				echo "--$val";<br />			}<br />			echo "<br />";<br />		}<br />	}<br />	if(!is_bool($res))<br />	{<br />		$res->free();<br />	}<br />	$mysqli->close();<br />?>

为啥会报错：Commands out of sync; you can't run this command now
 这句报错，对应的查询语句是
$sql = "select * from login";
$res = $mysqli->query($sql);

非常不解，请答案，没百度到。
------解决方案--------------------
先把multi_query的结果集释放了,再进行查询