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 9SAE_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 10SAE_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 28SAE_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

?>
  <?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~