The output control function gives you the freedom to control the outputs of the data in your script. It is very useful, especially when you want to output a file header after the data has been output. The output control function does not affect the header information sent using header () or Setcookie (), only data blocks that resemble Echo () and PHP code are useful. Let's start with a simple example that gives you a general impression of the output control:
Example 1.
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
?>
All people who know about the header () function know that this function sends a file header to the browser, but if there are any outputs (including null output, such as spaces, carriage returns, and line feeds) before using this function, an error is indicated. If we get rid of the first line of Ob_start () and execute the program, we'll find an error message: "Header had all ready to send by"! But with Ob_start, there is no hint of error, because when the buffer is opened, the character behind the echo is not output to the browser, but remains on the server until you use flush or ob_end_flush to output, so there will be no file header output error!
Introduction of related functions
1, Flush: Flush the contents of the buffer, output.
function format: Flush ()
Description: This function is often used and is highly efficient.
2. Ob_start: Open Output buffer
function format: void Ob_start (void)
Note: When the buffer is active, all non-file header information from the PHP program is not sent, but is saved in the internal buffer. In order to output the contents of the buffer, you can use the contents of the Ob_end_flush () or flush () output buffers.
3. Ob_get_contents: Returns the contents of the internal buffer.
How to use: String ob_get_contents (void)
Description: This function returns the contents of the current buffer and returns FALSE if the output buffer is not activated.
4. Ob_get_length: Returns the length of the internal buffer.
How to use: int ob_get_length (void)
Note: This function returns the length of the current buffer, as with ob_get_contents, if the output buffer is not activated. FALSE is returned.
5. Ob_end_flush: Sends the contents of the internal buffer to the browser, and closes the output buffer.
How to use: void Ob_end_flush (void)
Description: This function sends the contents of the output buffer (if any).
6. Ob_end_clean: Delete the contents of the internal buffer and close the internal buffer
How to use: void Ob_end_clean (void)
Description: This function does not output the contents of the internal buffer but deletes it!
7. Ob_implicit_flush: Turn absolute refresh on or off
How to use: void Ob_implicit_flush ([int flag])
Description: People who have used Perl know the meaning of $|=x, this string can open/close the buffer, and the Ob_implicit_flush function is the same, the default is to close the buffer, open the absolute output, each script output is sent directly to the browser, no longer need to call flush ()
Second, in-depth understanding 1. About the Flush function:
This function appears in PHP3, is a very efficient function, and he has a very useful function is to refresh the browser cache. Let's give an example of a very obvious running effect that illustrates flush.
Example 2. for($i = 1; $i <= 300; $i++) print(" ");
// 这一句话非常关键，cache的结构使得它的内容只有达到一定的大小才能从浏览器里输出
// 换言之，如果cache的内容不达到一定的大小，它是不会在程序执行完毕前输出的。经
// 过测试，我发现这个大小的底限是256个字符长。这意味着cache以后接收的内容都会
// 源源不断的被发送出去。
for($j = 1; $j <= 20; $j++) {
echo $j . "
";
flush(); //这一部会使cache新增的内容被挤出去，显示到浏览器上
sleep(1); //让程序"睡"一秒钟，会让你把效果看得更清楚
}
?> Specific effects you can come here and see http://www.php2000.com/~uchinaboy/out.php.
PHP2000 's newest PHP chat room is the use of this technology, unfortunately, the source code is not public L
Note: If you open an absolute refresh by adding Ob_implicit_flush () to the program's header, you can no longer use flush () in your program, and the benefit is: increase efficiency!
2. About OB series functions:
I'd like to cite an example of my good friend y10k first:
Example 3.
For example, you use the server and client settings information, but this information is different from the client, if you want to save the Phpinfo () function output what to do? Before there is no buffer control, it can be said that there is no way, but with the control of the buffer, we can easily solve:
ob_start(); //打开缓冲区
phpinfo(); //使用phpinfo函数
$info = ob_get_contents(); //得到缓冲区的内容并且赋值给$info
$file = fopen('info.txt', 'w'); //打开文件info.txt
fwrite($file, $info); //写入信息到info.txt
fclose($file); //关闭文件info.txt
?> Using the above method, you can save the Phpinfo information of different users, which in the past I am afraid there is no way to do! In fact, the above is a few "process" into the "function" Method!
One might ask, "is that what it looks like?" Is there any other use? "Of course, such as the author of the Forum's PHP syntax highlighting is related to this (php default syntax highlighting function will be directly output, can not save the results, if every call is likely to be a waste of CPU, the author's forum to the syntax highlighting function display results with the method of control buffer), If you're interested, you can take a look at http://www.zphp.com/bbs/!. Perhaps now you have a certain understanding of the function of Ob_start (), the above example seems simple, but actually has mastered the use of Ob_start () points.
<1>: Use Ob_start to open the browser cache, which guarantees that the contents of the cache will not be output until you call Flush (), Ob_end_flush () (or the program finishes).
<2> Now you should know the advantages you have: You can use the Header,setcookie and session after any output, which is a great feature of Ob_start, or you can use the Ob_start parameters after the cache is written , and then run the command automatically, such as Ob_start ("Ob_gzhandler"), and our most common practice is to use ob_get_contents () to get the contents of the cache and then process it ...
<3> When processing is complete, we can use various methods to output, flush (), Ob_end_flush (), and wait until the program finishes executing the automatic output. Of course, if you use Ob_get_contents (), then you have to control the output mode. Here, let's see what we can do with OB series functions ...
(a), static template technology
Introduction: The so-called static template technology is in some way, so that users on the client side is generated by PHP HTML page. If this HTML page is not updated again, then when another user browses to the page again, the program will no longer invoke PHP and the associated database, for some of the more informative sites, such as Sina,163,sohu. The benefits of a technology like this are enormous. There are two ways I know to implement static output:
<1>. A template.inc.php class implementation that modifies Phplib by y10k.
<2> Use the OB series function implementation.
For the first method, because it is not the issue to be studied in this article, so don't repeat it.
Let's take a look at the concrete implementation of the second approach:
Example 4. ob_start();//打开缓冲区
?>
Full output of PHP page
$content = ob_get_contents(); //取得php页面输出的全部内容
$fp = fopen("output00001 . html", "w"); //创建一个文件，并打开，准备写入
fwrite($fp, $content); //把php页面的内容全部写入output00001.html，然后……
fclose($fp);
?>
In this way, the so-called static template is easily implemented ...
(ii), capture output The above example 4. Is the simplest case, you can also work on the $content before writing ...
You can try to catch some keywords and then go back to it, such as Example 3. The PHP syntax is highlighted. Personally think that this function is the biggest essence of this function, it can solve a variety of problems, but need you have enough imagination ...
Example 5.
function run_code($code) {
If ($code) {
ob_start();
eval($code);
$contents = ob_get_contents();
ob_end_clean();
} else {
echo "错误！没有输出";
exit();
}
return $contents;
}
?> The use of this example is not very large, but the typical $code itself is a variable output page, and this example uses eval to replace the variables in the $code, and then the output to capture the output, and then once the processing ... Example 6. Faster transfer /*
* * Title ...: PHP4 HTTP Compression Speeds up the Web
* * Version ...: 1.20
* * Author ...: catoc
* * Filename ...: gzdoc.php
* * Last changed: 18/10/2000
* * Requirments ...: PHP4 >= 4.0.1
* * PHP was configured with--with-zlib[=dir]
* * Notes ...: Dynamic Content acceleration Compresses
* * The data transmission data on the fly
* * Code by Sun Jin Hu (Catoc)
* * Most newer browsers since 1998/1999 has
* * been equipped to support the HTTP 1.1
* * Standard known as "content-encoding."
* * Essentially the browser indicates to the
* * Server that it can accept "content encoding"
* * And if the server is capable it would then
* * Compress the data and transmit it. The
* * Browser decompresses it and then renders
* * the page.
**
* * Modified by John Lim (jlim@natsoft.com.my)
* * Based on ideas by Sandy McArthur, Jr
* * Usage .....:
* * No Space before the beginning of the first ' * *------------Start of File----------
** | ** | Include (' gzdoc.php ');
** |? >
** |
* * | ... the page ...
** |
** | ** | Gzdocout ();
** |? >
* *-------------End of File-----------
*/
Ob_start ();
Ob_implicit_flush (0);
function Checkcangzip () {
Global $HTTP _accept_encoding;
if (headers_sent () | | connection_timeout () | | connection_aborted ()) {
return 0;
}
if (Strpos ($HTTP _accept_encoding, ' X-gzip ')!== false) return "X-gzip";
if (Strpos ($HTTP _accept_encoding, ' gzip ')!== false) return "gzip";
return 0;
}
/* $level = Compression level 0-9, 0=none, 9=max */
function Gzdocout ($level = 1, $debug = 0) {
$ENCODING = Checkcangzip ();
if ($ENCODING) {
Print "n n ";
$Contents = Ob_get_contents ();
Ob_end_clean ();
if ($debug) {
$s = " This is CATOC a long time code, is seen in Weblogs.com, he took advantage of the zlib function, the content of the transmission of compression, testing shows that for more than 10k pages, will produce effects, and the larger the page, the more obvious effect ... Not compress length: " . strlen($Contents);
$s .= "Compressed length: " . strlen(gzcompress($Contents, $level));
$Contents .= $s;
}
header("Content-Encoding: $ENCODING");
print "x1fx8bx08x00x00x00x00x00";
$Size = strlen($Contents);
$Crc = crc32($Contents);
$Contents = gzcompress($Contents, $level);
$Contents = substr($Contents, 0, strlen($Contents) - 4);
print $Contents;
print pack('V', $Crc);
print pack('V', $Size);
exit;
} else {
ob_end_flush();
exit;
}
}
?>
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