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HomeBackend DevelopmentPHP TutorialPHP:Cannot modify header information

ob_start();
setcookie("username","test",time()+3600);
echo "the username is:".$HTTP_COOKIE_VARS["username"]."\n";
echo "the username is:".$_COOKIE["username"]."\n";
print_r($_COOKIE);
?>
访问该PHP文件时提示Warning: Cannot modify header information - headers already sent by出错的原因
原因是在php程序的头部加了,header("content-type: text/html; charset=utf-8");之后页面就出现上面的错误。上网查了一些资料,说是我的php.ini里面的配置出了问题,找到php.ini文件中的output_buffering默认为off的,把它改为on或者任意一个数字,但尝试无结果。

setcookie函数必?在任何资料输出至浏览器前,就先送出
基于上面?些限制,所以?行setcookie()函数时,常会碰到"Undefined index"、"Cannot modify header information - headers already sent by"…等问题,解?"Cannot modify header information - headers already sent by"????的方法是在产生cookie前,先延缓资料输出至浏览器,因此,您可以在程式的最前方加上ob_start()函?。


ob_start()函数用于打开缓冲区,比如header()函数之前如果就有输出,包括回车\空格\换行\都会有"Header had all ready send by"的错误,这时可以先用ob_start()打开缓冲区PHP代码的数据块和echo()输出都会进入缓冲区而不会立刻输出:

通过以下方法,问题得到解决:

//在header()之前

ob_start(); //打开缓冲区 
echo \"Hellon\"; //输出 
header("location:index.php"); //把浏览器重定向到index.php 
ob_end_flush();//输出全部内容到浏览器 
?>

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