假設有如下代碼：
<?php
for ($i=10; $i>0; $i--) {
echo $i;
flush();
sleep(1);
}
?>按代碼理解似乎應該是每過1秒鐘，將輸出一個數字，從10~1 (運行時間>10ms)
而使用nginx作爲web服務器時，會發現上面的代碼，在程序運行10ms後一次性輸出了10~1
通過搜索，找到一段如下的說明：
Nginx的FastCGI環境中，如果數據小於fastcgi_buffers，會緩存到內存中，如果數據小於fastcgi_max_temp_file_size，會緩存到硬盤上。
但在實際的例子中，我發現，只要我緩存中的字符串長度大於等於php.ini中output_buffering設定的值，flush還是有作用的。
示例Demo就是類似於Facebook的BigPipe(點此查看Facebook網站的Ajax化、緩存和流水線PDF>>)，文章參考了(利用bigpipe機制實現頁面模塊的異步渲染)
在我下載的PHP中，它的配置文件php.ine中output_buffering的值被設定爲4096
; Note: Output buffering can also be controlled via Output Buffering Control ; functions. ; Possible Values: ; On = Enabled and buffer is unlimited. (Use with caution) ; Off = Disabled ; Integer = Enables the buffer and sets its maximum size in bytes. ; Note: This directive is hardcoded to Off for the CLI SAPI ; Default Value: Off ; Development Value: 4096 ; Production Value: 4096 ; http://php.net/output-buffering output_buffering = 4096
測試例子在Windows下測試通過(nginx/0.7.59、PHP 5.3.4)
1ms左右可以看到完整的頁面
對應的HTML結構
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>BigPipe Demo 3</title>
<style type="text/css">
* {margin: 0; padding:0;}
body {background-color:#fff;}
div{border:2px solid #4F81BD; margin:30px; padding: 10px;}
p {word-wrap:break-wrod; word-break:break-all; color: #666;}
.red {color: #f00;}
.blue {color:blue;}
.green {color:green;}
</style>
<script> 1: 2: function render(nodeID,html){ 3: document.getElementById(nodeID).innerHTML=html; 4: }</script>
</head>
<body>
<div id="header"><p>Loading...</p></div>
<div id="content"><p>Loading...</p></div>
<div id="footer"><p>Loading...</p></div>
<script>render('header', '<p><span class="blue">111111</span> 返回的頭部信息
HTTP/1.1 200 OK Server: nginx/0.7.59 Date: Fri, 01 Jul 2011 17:01:00 GMT Content-Type: text/html; charset=utf-8 Transfer-Encoding: chunked Connection: keep-alive X-Powered-By: PHP/5.3.4
11ms後header區域被初始化，將顯示1111
21ms後，content、footer渲染完成，整個頁面也就呈現出來了
(其實這裏有點奇怪，和預期的不大相符，預期從進入頁面開始計時1ms後顯示111111，11ms後顯示222222，21ms後才顯示333333，而這裏222222、333333是同時在21ms後渲染出來的，我想還是nginx的緩存上有點問題~)
整個頁面被分成5塊輸出
塊與塊之間有標識符，如下所示：
fbc
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>BigPipe Demo 3</title>
<style type="text/css">
* {margin: 0; padding:0;}
body {background-color:#fff;}
div{border:2px solid #4F81BD; margin:30px; padding: 10px;}
p {word-wrap:break-wrod; word-break:break-all; color: #666;}
.red {color: #f00;}
.blue {color:blue;}
.green {color:green;}
</style>
<script> 1: 2: function render(nodeID,html){ 3: document.getElementById(nodeID).innerHTML=html; 4: }</script>
</head>
<body>
<div id="header"><p>Loading...</p></div>
<div id="content"><p>Loading...</p></div>
<div id="footer"><p>Loading...</p></div>
<script> 1: render('header', '<p><span class="blue">111111</span> 2: ff6 3: <p>');</script>
<script> 1: render('content', '<p><span class="red">222222</span> 2: ff7 3: <p>');</script>
<script> 1: render('footer', '<p><span class="green">333333</span> 2: 34d 3: <p>');</script>
</body>
</html>
0整個測試頁面的源文件php也很簡單：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>BigPipe Demo 3</title>
<style type="text/css">
* {margin: 0; padding:0;}
body {background-color:#fff;}
div{border:2px solid #4F81BD; margin:30px; padding: 10px;}
p {word-wrap:break-wrod; word-break:break-all; color: #666;}
.red {color: #f00;}
.blue {color:blue;}
.green {color:green;}
</style>
<script>
function render(nodeID,html){
document.getElementById(nodeID).innerHTML=html;
}
</script>
</head>
<body>
<div id="header"><p>Loading...</p></div>
<div id="content"><p>Loading...</p></div>
<div id="footer"><p>Loading...</p></div>
<?php
ob_flush();
flush();
sleep(1);
//填充緩衝區
$header = str_pad('<span class="blue">111111</span>', 4096);
?>
<script>render('header', '<p><?php echo $header;?><p>');</script>
<?php
ob_flush();
flush();
sleep(10);
$content = str_pad('<span class="red">222222</span>', 4096);
?>
<script>render('content', '<p><?php echo $content;?><p>');</script>
<?php
ob_flush();
flush();
sleep(10);
$footer = str_pad('<span class="green">333333</span>', 4096);
?>
<script>render('footer', '<p><?php echo $footer;?><p>');</script>
<?php
ob_flush();
flush();
?>
</body>
</html>