ob_end_flush()

(PHP 4, PHP 5, PHP 7)

冲刷出（送出）输出缓冲区内容并关闭缓冲

说明

ob_end_flush(void): bool

这个函数将送出最顶层缓冲区的内容（如果里边有内容的话），并关闭缓冲区。如果想进一步处理缓冲区中的内容，必须在ob_end_flush()之前调用ob_get_contents()，因为在调用ob_end_flush()后缓冲区内容被丢弃。

Note:这个函数与ob_get_flush()相似，不同的是ob_get_flush()会把缓冲区中的内容作为字符串返回。

返回值

成功时返回TRUE，或者在失败时返回FALSE。错误的原因首先是，在调用时没有一个起作用的缓冲区，或者是因为某些原因缓冲区不能被删除（可能对特殊缓冲区而言）。

错误／异常

如果函数失败了，将引发一个E_NOTICE异常。

更新日志

版本	说明
4.2.0	添加了布尔返回值。

范例

Example #1ob_end_flush()example

下面的例子给出了一种送出缓冲区内容并关闭所有输出缓冲区的容易的方法：

<?php
  while (@ob_end_flush());
?>

参见

ob_start() 打开输出控制缓冲
ob_get_contents() 返回输出缓冲区的内容
ob_get_flush() 刷出（送出）缓冲区内容，以字符串形式返回内容，并关闭输出缓冲区。
ob_flush() 冲刷出（送出）输出缓冲区中的内容
ob_end_clean() 清空（擦除）缓冲区并关闭输出缓冲

A note on the above example...
with PHP 4 >= 4.2.0, PHP 5 you can use a combination of ob_get_level() and ob_end_flush() to avoid using the @ (error suppresion) which should probably be a little faaster.
<?php
while (ob_get_level() > 0) {
  ob_end_flush();
}
?>

best way to compress a css code:
<?php
 header('Content-type: text/css');
 ob_start("compress");
 function compress($buffer) {
  // remove comments
  $buffer = preg_replace('!/\*[^*]*\*+([^/][^*]*\*+)*/!', '', $buffer);
  // remove tabs, spaces, newlines, etc.
  $buffer = str_replace(array("\r\n", "\r", "\n", "\t", ' ', '  ', '  '), '', $buffer);
  return $buffer;
 }
 include('./template/main.css');
 include('./template/classes.css');
<?php
 ob_end_flush();
?>
Include in <head>:
<link rel="stylesheet" type="text/css" href="/design.php" media="all" />

Wanted to speed things up and put some processing after the page has been delivered to the client. That drove me almost insane, but finally, I found a solution (php 5.2.5):
<?php
ob_start(); // outer buffer
ob_start(); // inner buffer to catch URL rewrites and other post processing
session_start(); // registers URL rewriter with inner buffer!
echo '...';
// log performance data to log files *after* delivering the page!
register_shutdown_function(array($benchmarkclass,'log_perf_data'));
// now flush output output to client
ob_end_flush();
// need to calculate content length *after* URL rewrite!
header("Content-length: ".ob_get_length());
ob_end_flush();
// now we close the session and do some arbitrary clean-up tasks
// registered using register_shutdown_function()
session_write_close();
?>

Apart from being mostly redundant, ob_end_flush() can be downright damaging in some weird cases.
Actual example: a particular page on an Intranet website which would appear blank on Internet Explorer 6 when ob_start('ob_gzhandler') was called in the beginning and ob_end_flush() at the end.
We couldn't figure out what made that page special no matter what we tried. The ob_ functions were placed in scripts which were include()'d by all pages just the same, but only that page did this.
Even stranger, the problem only appeared on direct browser/server connections. Whenever the connection passed through a proxy the problem dissapeared. I'm guessing some kind of HTTP encoding headers mumbo-jumbo.
Solution: unless you really need it in particular cases, remove the ob_end_flush() call and rely on the builtin, automatic buffer flush.

If you enable zlib.output_compression then level count will be increased by 1 and then this code:
<?php while (ob_get_level()) { ob_end_clean(); } ?>
will just freeze your script.

It appears that you can call ob_end_flush() regardless of whether or not output buffering was ever started using ob_start(). This can prove useful because it saves you from having to create conditional statements based on whether a particular function or include file has started output buffering. You can simply call the ob_end_flush() anyway and if there's output in the buffer, it will be sent, otherwise your script will just keep on keepin' on.

It appears that ob_end_flush() is very important if you are looping. For instance if you are using a mass mailer that uses the output buffer for creating HTML content. Use ob_end_flush() to avoid server errors.

ob_end_flush() isn't needed in MOST cases because it is called automatically at the end of script execution by PHP itself when output buffering is turned on either in the php.ini or by calling ob_start().

Remember that chromium browser (and maybe other webkit-based browsers) have some issues with ob_end_flush.
http://code.google.com/p/chromium/issues/detail?id=31410
You may use
header("Content-Type: text/plain");
to solve those issues if you do not need html.