为啥PHP输出多出了特殊字符

	<br />        //校验用户名<br />	$userName = $_POST['username'];<br />	if(!preg_match('/^[0-9a-zA-Z]{3,16}$/', $userName)){<br />		die();<br />	}<br />	//判断用户是否已经存在<br />	require('./../inc/pdo_conn.php');<br />	$hPdoPre = $hPdo->prepare("SELECT user_name FROM user WHERE user_name=:username");<br />	$hPdoPre->bindParam(':username', $userName, PDO::PARAM_STR);<br />	$hPdoPre->execute();<br />	$result = $hPdoPre->fetchAll();<br /><br />	//如果为空则可以注册<br />	if(empty($result)){<br />		echo 'y';<br />	}else{<br />		echo 'n';<br />	}