ob_start() 和 ob_end_flush() 的 PHP 标头问题
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PHP Header issue with ob_start() and ob_end_flush()
提问by diEcho
I get header problem while I use ob_start()in the beginning of a page and ob_end_flush()at the end. Because I use header function after some query execution.
我ob_start()在页面开头和ob_end_flush()结尾使用时遇到标题问题。因为我在执行一些查询后使用了 header 函数。
ob_start();
include_once("header.php");
global $db;
$countstmt="SELECT COUNT(*) FROM tbl_lib_hours dh WHERE book_id IN(SELECT book_id FROM tbl_book WHERE user_id=".$_SESSION['uid'].") ";
$delHourExist=$db->query($countstmt);
if($delHourExist){
header("location:edit_delivery_hours.php");
}
....
include_once('footer.php');
ob_end_flush();
In header.phpthere I also added ob_start();and in footer.phpi added ob_end_flush();, but I think that is not problem, although other pages are running with same script I write above
在header.php 中，我还添加了ob_start(); 在footer.php 中我添加了ob_end_flush(); ，但我认为这不是问题，尽管其他页面正在使用我上面写的相同脚本运行
The error I am getting:
我得到的错误：
Warning: Cannot modify header information - headers already sent in D:\xampp\htdocs\project\add_book_hours.php on line 9
警告：无法修改标题信息 - 标题已发送到 D:\xampp\htdocs\project\add_book_hours.php 第 9 行
回答by Karsten
Is there any space before the first <?php?
第一个之前有空格<?php吗？
Is there an UTF8-BOM at the beginning of the file?
文件开头是否有 UTF8-BOM？
回答by Scott Saunders
There's a lot of invisible output in your code:
您的代码中有很多不可见的输出：
<?php ob_start();?> --- THERE IS A LINE RETURN HERE ---
--- SPACES OR TABS ---<?php include_once("header.php"); ?> --- LINE RETURN ---
--- AND HERE ---<?php global $db;
...
Quit starting and ending your php tags. Just do this:
退出开始和结束你的 php 标签。只需这样做：
<?php
ob_start();
include_once("header.php");
global $db;
...
Make absolutely sure that there is no output, and no whitespace outside of your tags before the call to ob_start(). If your error is on line 9, you've got a bunch of lines before that call that could be the problem. You may want to post all of those lines, numbered, so we can look at them carefully.
确保在调用 ob_start() 之前没有输出，并且标签外没有空格。如果您的错误出现在第 9 行，那么在该调用之前您有一堆可能是问题的行。您可能想要张贴所有这些行，编号，以便我们可以仔细查看它们。
回答by VolkerK
I'm a bit baffled the warning message doesn't include the location of the code that caused the first content to be sent to the client. The function headers_sent()can return that location, too. So, for debugging purposes, please try
我有点困惑，警告消息不包括导致第一个内容发送到客户端的代码的位置。函数headers_sent()也可以返回该位置。因此，出于调试目的，请尝试
if($delHourExist)
{
if ( headers_sent($path, $lineno) ) {
echo '<pre>Debug: output started at ', $path, ':', $lineno, "</pre>\n";
}
header("location: edit_delivery_hours.php");
}
回答by mariofertc
I resolve mi problem with some white spaces in my script with ob_start(); ob_end_flush(); and ob_end_clean();
So you could test your code
我使用 ob_start() 解决了脚本中一些空格的问题；ob_end_flush(); 和 ob_end_clean(); 所以你可以测试你的代码
<?php
ob_start();
include_once("header.php");
global $db;
$countstmt="SELECT COUNT(*) FROM tbl_lib_hours dh WHERE book_id IN(SELECT book_id FROM tbl_book WHERE user_id=".$_SESSION['uid'].")";
$delHourExist=$db->query($countstmt);
if($delHourExist)
{
ob_end_flush();
ob_end_clean();
header("location:edit_delivery_hours.php");
}
include_once('footer.php');
?>
<?php
ob_start();
include_once("header.php");
global $db;
$countstmt="SELECT COUNT(*) FROM tbl_lib_hours dh WHERE book_id IN(SELECT book_id FROM tbl_book WHERE user_id=".$_SESSION['uid'].")";
$delHourExist=$db->query($countstmt);
if($delHourExist)
{
ob_end_flush();
ob_end_clean();
header("location:edit_delivery_hours.php");
}
include_once('footer.php');
?>
回答by Kibbee
I think the problem may be that you are trying to change the headers, after you have already sent something else to the output. Even when using buffering, I don't think this is possible. I think you need to call ob_end_clean() to discard the current buffer and write header information.
我认为问题可能在于您在将其他内容发送到输出之后尝试更改标题。即使使用缓冲，我也不认为这是可能的。我认为您需要调用 ob_end_clean() 来丢弃当前缓冲区并写入头信息。
