我得到的错误：
Cannot modify header information - headers already sent by (output started at
/home/spikes/public_html/index.php:17) in /home/spikes/public_html/functions.php on line 58
的index.php：
<body>
<section id="mainWrapper">
<section>
<h1>Spikes.co.il</h1>
</section>
<?php include('nav.php');?> //line 17
....
function.php：
function createSession($userid,$firstname)
{
$expire=time()+60*60*24*30;
setcookie("usid", $userid, $expire);
setcookie("usname", $firstname, $expire);
}
我真的不明白为什么会这样......