无法发送会话Cookie - 已发送的标头 [英] Cannot send session cookie - headers already sent

问题描述

可能存在重复：

已由PHP发送的头文件

下面是一个简单的例子我的PHP代码（我希望如此）是自我解释。我试图做的是更新会话变量。但是脚本的输出如下：

lockquote
警告：session_start（）
[function.session-start]：不能发送
会话cookie - 头文件已经发送
（输出开始于
/Library/WebServer/Documents/facebook/test.php:8）
in
/ Library /WebServer/Documents/facebook/test.php第11行

警告是由 echo 语句当然是在第8行和第9行。是否有任何简单的解决方案来阻止此警告。

感谢任何指针，Andrej

 <？php 
 session_start（）; 
 $ _SESSION ['percent'] = 0; 
 $ iterations = 50; （$ i = 0; $ i <= iterations; $ i ++）{
 $ percent =（$ i / $ iterations）* 100; 
 
; 
回声Hello World！; 
回声< br />; 
 //更新会话变量
 session_start（）; 
 $ _SESSION ['percent'] = number_format（$ percent，0，''，''）; 
 session_commit（）; 
} 
？> 
  

对我而言，唯一可行的解​​决方案是（即更新会话变量）：

 <？php 
 ob_start（）; 
 session_start（）; 
 $ _SESSION ['percent'] = 0; 
 $ iterations = 50; （$ i = 0; $ i <= 50; $ i ++）{
 $ percent =（$ i / $ iterations）* 100; 
 
; 
回声Hello World！; 
回声< br />; 
 //更新会话变量
 session_start（）; 
 $ _SESSION ['percent'] = number_format（$ percent，0，''，''）; 
 session_commit（）; 
} 
 ob_flush（）; 
？> 
  

这很丑陋，它先缓冲输出...

解决方案

开始输出后，无法设置cookie（或发送任何其他标题）。您可以在第1行添加ob_start（）来缓冲输出。

正确的解决方案是将逻辑从输出中分离出来。查看例如
http://www.paragoncorporation.com/ArticleDetail.aspx?ArticleID=21

Possible Duplicate:
Headers already sent by PHP

Below is a simple example of my PHP code which (I hope so) is self explanatory. What I try to do is to update the session variable. But the output of the script is as follows:

Warning: session_start() [function.session-start]: Cannot send session cookie - headers already sent by (output started at /Library/WebServer/Documents/facebook/test.php:8) in /Library/WebServer/Documents/facebook/test.php on line 11

The warning is caused by the echo statements in line 8 and 9, of course. Is there any simple solution to stop this warning.

Thanks for any pointers, Andrej

<?php
session_start();
$_SESSION['percent'] = 0;
$iterations = 50;

for ($i = 0; $i <= iterations; $i++) {
  $percent = ($i / $iterations) * 100;
  echo "Hello World!";
  echo "<br />";
  // update session variable
  session_start();
  $_SESSION['percent'] = number_format($percent, 0, '', '');
  session_commit();
}
?>

The only solution that works (i.e. updates the session variable) for me is:

<?php
ob_start();
session_start();
$_SESSION['percent'] = 0;
$iterations = 50;

for ($i = 0; $i <= 50; $i++) {
  $percent = ($i / $iterations) * 100;
  echo "Hello World!";
  echo "<br />";
  // update session variable
  session_start();
  $_SESSION['percent'] = number_format($percent, 0, '', '');
  session_commit();
}
ob_flush();
?>

It's ugly, while it buffers the output first...

解决方案

It's not possible to set cookies (or send any other headers) after output is started. You could add ob_start() at line 1 to buffer the output.

The right solution is to separate logic from the output. Check out e.g. http://www.paragoncorporation.com/ArticleDetail.aspx?ArticleID=21

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