提示「headers already sent by」是怎么回事?错误位置如下

Question

错误提示:
SAE_Warning: Cannot modify header information - headers already sent by (output started at /data1/www/htdocs/345/leank/1/bbs/login.php:15) in bbs/login.php on line 9

SAE_Warning: Cannot modify header information - headers already sent by (output started at /data1/www/htdocs/345/leank/1/bbs/login.php:15) in bbs/login.php on line 10

SAE_Warning: Cannot modify header information - headers already sent by (output started at /data1/www/htdocs/345/leank/1/bbs/login.php:15) in bbs/login.php on line 28

SAE_Warning: Cannot modify header information - headers already sent by (output started at /data1/www/htdocs/345/leank/1/bbs/login.php:15) in bbs/login.php on line 29

大致的代码:

<?php/*
* 未完成内容 : 添加判断的url中log?= "" 的if语句,来判断用户是登陆还是退出
*添加一个判断是否已经登陆的if语句
*
*/include("conn.php");function clearcookies(){    setCookie('username','',time()-3600);    setCookie('logset','',time()-3600);
}?>
  <?php
    if ($_POST['loginsubmit'])  //检查是否提交
    {        clearcookies();        $sql = "SELECT * FROM user WHERE username = '$_POST[username]'";        $query = mysql_query($sql);        $userinfo = mysql_fetch_array($query);        if ($_POST[password] != "" & $_POST[username] != "") //检查用户名密码是否填写
        {            if ($userinfo['password'] == $_POST['password'] ) //在SQL中检查用户名密码是否正确
            {                $username = $_POST[username];                
                setcookie('username','$username',time()[phone],'/');                setcookie('logset','ok',time()[phone],'/');                echo "<meta http-equiv=refresh content=0;url=index.php?foo=$_POST[username]>";
            }            else
            {                echo "登录失败!";                echo "请检查您的用户名或密码是否都填写正确";
            }
        }        else
        {            echo "登录失败!";            echo "请检查您的用户名或密码是否为空";
        }
    }  ?>

处错误的大致是这个位置:
setcookie('username','$username',time()[phone],'/');
setcookie('logset','ok',time()[phone],'/');

Answer 1

因为在setCookie之前多输出了东西造成的，看代码似乎是输出了空格，把中间的?> &nbsp;&nbsp;<?php去掉应该就可以了

Answer 2

亲爱的.记得每次写完程序后把文件保存成UTF-8 无BOM格式哦.否则就容易出现这样的错误的说~