How does the PHP page be buffered?

PHP has a lot of mechanisms, functions, in fact, is the magician, repeated play good, in fact, even simple application, will appear magical effect. Brother even PHP training here is a ob_start () function.
The Ob_start () function is used to open the buffer, such as the header () function, if there is output, including carriage return \ space \ newline \ will have "Header had all ready to send by" error, you can first use Ob_start () The data Block and Echo () output that open the buffer PHP code will go into the buffer without immediately outputting it. Of course, opening the buffer is a lot of work, just play your imagination. You can summarize the following four points:
1. Before header ()
Ob_start (); Open buffer
echo \ "Hellon\"; Output
Header ("location:index.php"); redirect the browser to index.php
Ob_end_flush ();//output all content to the browser
?>
The 2.phpinfo () function obtains information on both the client and server side, but the way to save the client information with buffers is the best choice.
Ob_start (); Open buffer
Phpinfo (); Using the Phpinfo function
$info =ob_get_contents (); Get the contents of the buffer area and assign it to $info
$file =fopen (\ ' info.txt\ ', \ ' w\ '); Open File Info.txt
Fwrite ($file, $info); Write information to Info.txt
Fclose ($file); Close File Info.txt
?>
3. Static page Technology
Ob_start ();//Open buffer
?>
Full output of PHP page
$content = Ob_get_contents ();//Get all the contents of the PHP page output
$fp = fopen ("output00001.html", "w"); Create a file, and open it, ready to write
Fwrite ($fp, $content); Write the contents of the PHP page to output00001.html, then ...
Fclose ($FP);
?>
4. Output code
Function Run_code ($code) {
If ($code) {
Ob_start ();
eval ($code);
$contents = Ob_get_contents ();
Ob_end_clean ();
}else {
echo "Error! No output";
Exit ();
}
return $contents;
}
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.
code<?php
Ob_start (); Open buffer
echo \ "Hellon\"; Output
Header ("location:index.php"); redirect the browser to index.php
Ob_end_flush ();//output all content to the browser
?>
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 will 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 $|=x, this string can open/close the buffer, and the Ob_implicit_flush function is the same, the default is to close the buffer, open the absolute output, each script output is sent directly to the browser, no longer need to call flush ()
Second, in-depth understanding:
1. About the Flush function:
This function appears in PHP3, is a very efficient function, and he has a very useful function is to refresh the browser cache. Let's give an example of a very obvious running effect that illustrates flush.
Example 2.
code<?php
for ($i = 1; $i <=, $i + +) print ("");
This sentence is very key, the structure of the cache so that its content can only reach a certain size to be exported from the browser
In other words, if the content of the cache does not reach a certain size, it will not be output until the program finishes executing. By
After testing, I found that the bottom limit of this size is 256 characters in length. This means that content received by the cache will be
The stream was sent out.
for ($j = 1; $j <=; $j + +) {
echo $j. "
“;
Flush (); This will cause the cache additions to be squeezed out and displayed on the browser
Sleep (1); Let the program "Sleep" a second, will let you see the effect more clearly
}
?>
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 can use the server and client settings information, but this information will be different from the client, if you want to save the Phpinfo () function output what to do? Before there is no buffer control, there is no way to say, but with the control of the buffer, we can easily solve:
code<?php
Ob_start (); Open buffer
Phpinfo (); Using the Phpinfo function
$info =ob_get_contents (); Get the contents of the buffer area and assign it to $info
$file =fopen (\ ' info.txt\ ', \ ' w\ '); Open File Info.txt
Fwrite ($file, $info); Write information to Info.txt
Fclose ($file); Close File 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 the way to convert some "process" to "function"!
Maybe someone would 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 the control buffer is retained), 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&gt: 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 Header,setcookie and the 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 ...
First, 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&gt. 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.
code<?php
Ob_start ();//Open buffer
?>
Full output of PHP page
<?
$content = Ob_get_contents ();//Get all the contents of the PHP page output
$fp = fopen ("output00001.html", "w"); Create a file, and open it, ready to write
Fwrite ($fp, $content); Write the contents of the PHP page to output00001.html, then ...
Fclose ($FP);
?>
In this way, the so-called static template is easily implemented ...
Second, capture the output
The above example 4. Is the simplest case, you can also work on the $content before writing ...
You can try to catch some keywords and then go back to it, such as Example 3. The PHP syntax is highlighted. Personally think that this function is the biggest essence of this function, it can solve a variety of problems, but need you have enough imagination ...
Example 5.
code<?
Function Run_code ($code) {
If ($code) {
Ob_start ();
eval ($code);
$contents = Ob_get_contents ();
Ob_end_clean ();
}else {
echo "Error! No output";
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
code<?
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 ($HTTP _accept_encoding,\ ' gzip\ ')!== false) return \ "Gzip\";
return 0;
}
function Gzdocout ($level =1, $debug =0) {
$ENCODING = Checkcangzip ();
if ($ENCODING) {
Print \ "N<!–use compress $ENCODING –>n\";
$Contents = Ob_get_contents ();
Ob_end_clean ();
if ($debug) {
$s = \ "<p>not compress length: \". strlen ($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
}
}
?>
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 ...

How does the PHP page be buffered?