为什么需要`str_pad(''，4096)`才能使PHP刷新正常工作? [英] Why do I need `str_pad('',4096)` to make PHP flushing work?

问题描述

例如，

这不起作用(Firefox 21，IE8):

this doesn't work (Firefox 21, IE8):

<?php
function flush_buffers(){
    ob_end_flush();
    ob_flush();
    flush();
    ob_start();
}  
ob_start();
echo 'Text 1<br />';
flush_buffers();
Sleep(2);
echo 'Text 2<br />';
flush_buffers();
Sleep(2);
echo 'Text 3<br />';
flush_buffers();
Sleep(2);
echo 'Text 4<br />';
?>

但这一项有效:

<?php
function flush_buffers(){
    echo str_pad('',4096);
    ob_end_flush();
    ob_flush();
    flush();
    ob_start();
}  
ob_start();
echo 'Text 1<br />';
flush_buffers();
Sleep(2);
echo 'Text 2<br />';
flush_buffers();
Sleep(2);
echo 'Text 3<br />';
flush_buffers();
Sleep(2);
echo 'Text 4<br />';
?>

我有在Win XP SP3上运行的PHP 5.4.11 VC9和Apache 2.4.3(apacheLounge).

I have PHP 5.4.11 VC9 and Apache 2.4.3 (apacheLounge) running on Win XP SP3.

推荐答案

某些浏览器包括其自己的内部缓冲区，以便以更少的断断续续下载和显示效率.在大多数情况下，此缓冲区为4Kb或4096字节.

Some browsers include their own internal buffer in order to download and display more efficiently with less choppiness. In most cases, this buffer is 4Kb, or 4096 bytes.

str_pad('',4096)的作用是在输出中写入4,096个空格.由于是HTML，因此这些空间会合并为一个空间.

What str_pad('',4096) does is write 4,096 spaces to the output. Since it's HTML, these spaces collapse into a single space.

总体而言，不应依赖此行为.浏览器用于查看网页，而不是混入控制台终端.

Overall, this behaviour should NOT be relied upon. Browsers are for viewing webpages, not bastardising into console terminals.

此外，为什么还要写</br>?没有结尾<br>标签，并且自动关闭的版本是<br />

Also, why are you writing </br>? There is no such thing as an end <br> tag, and the self-closing version is <br />

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