PHP: Output Control Functions - Manual

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Last updated: Sat, 27 Jan 2007

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# CXII. Output Control Functions

# Введение

The Output Control functions allow you to control when output is sent from the script. This can be useful in several different situations, especially if you need to send headers to the browser after your script has began outputting data. The Output Control functions do not affect headers sent using header() or setcookie(), only functions such as echo() and data between blocks of PHP code.

> Замечание: When upgrading from PHP 4.1 (and 4.2) to 4.3 due to a bug in earlier versions you must ensure that `implict_flush` is `OFF` in your `php.ini`, otherwise any output with ob_start() will not be hidden from output.

# Требования

Эти функции всегда доступны.

# Установка

Для использования этих функций не требуется проведение установки, поскольку они являются частью ядра PHP.

# Настройка во время выполнения

Поведение этих функций зависит от установок в `php.ini`.

Таблица 1. Output Control configuration options

Name | Default | Changeable | Changelog
--- | --- | --- | ---
output_buffering | "0" | PHP_INI_PERDIR |
output_handler | NULL | PHP_INI_PERDIR | Available since PHP 4.0.4.
implicit_flush | "0" | PHP_INI_ALL | PHP_INI_PERDIR in PHP <= 4.2.3.

Для подробного описания констант PHP_INI_*, обратитесь к документации функции ini_set().

Краткое разъяснение конфигурационных директив.

`output_buffering` boolean/integer

  You can enable output buffering for all files by setting this directive to 'On'. If you wish to limit the size of the buffer to a certain size - you can use a maximum number of bytes instead of 'On', as a value for this directive (e.g., output_buffering=4096). As of PHP 4.3.5, this directive is always Off in PHP-CLI.

`output_handler` string

  You can redirect all of the output of your scripts to a function. For example, if you set output_handler to mb_output_handler(), character encoding will be transparently converted to the specified encoding. Setting any output handler automatically turns on output buffering.

  > Замечание: You cannot use both mb_output_handler() with ob_iconv_handler() and you cannot use both ob_gzhandler() and zlib.output_compression.

  > Замечание: Only built-in functions can be used with this directive. For user defined functions, use ob_start().

`implicit_flush` boolean

  `FALSE` by default. Changing this to `TRUE` tells PHP to tell the output layer to flush itself automatically after every output block. This is equivalent to calling the PHP function flush() after each and every call to print() or echo() and each and every `HTML` block.

  When using PHP within an web environment, turning this option on has serious performance implications and is generally recommended for debugging purposes only. This value defaults to `TRUE` when operating under the `CLI SAPI`.

  See also ob_implicit_flush().

# Типы ресурсов

Данное расширение не определяет никакие типы ресурсов.

# Предопределенные константы

Данное расширение не определяет никакие константы.

# Примеры

Пример 1. Output Control example

`<?php
ob_start();
echo "Hello\n";
setcookie("cookiename", "cookiedata");
ob_end_flush();
?>`

In the above example, the output from echo() would be stored in the output buffer until ob_end_flush() was called. In the mean time, the call to setcookie() successfully stored a cookie without causing an error. (You can not normally send headers to the browser after data has already been sent.)

# Смотрите также

See also header() and setcookie().

add a note User Contributed Notes
Output Control Functions
basicartsstudios at hotmail dot com
28-Jan-2007 12:45
`Please note that most browsers don't display a table unless they passed its end-tag "</table>".
Thats why using this feature in HTML-tables might not result in what you expected...
best regards
BasicArtsStudios`
basicartsstudios at hotmail dot com
21-Jan-2007 10:39
`Sometimes you might not want to include a php-file under the specifications defined in the functions include() or require(), but you might want to have in return the string that the script in the file "echoes".
Include() and require() both directly put out the evaluated code.
For avoiding this, try output-buffering:
<?php
ob_start();
eval(file_get_contents($file));
$result = ob_get_contents();
ob_end_clean();
?>
or
<?php
ob_start();
include($file);
$result = ob_get_contents();
ob_end_clean();
?>
which i consider the same, correct me if I'm wrong.
Best regards, BasicArtsStudios`
trucex [um, at] gmail [um, dot] com
16-Sep-2006 02:08
`Unfortunately, the PHP guys didn't build support into any of the image output functions to return the image instead of outputting it.
Fortunately, we have output buffering to fix that.
<?
$im = imagecreatetruecolor(200, 200);
// Other image functions here...
ob_start();
imagepng($im);
$imageData = ob_get_contents();
ob_clean();
?>
You can now use the $imageData variable to either create another GD image, save it, put it in a database, make modifications to the binary, or output it to the user. You can easily check the size of it as well without having to access the disk...just use strlen();`
webmaster at wistex dot com
07-Sep-2006 04:07
`Now this just blew my mind. I had a problem with MySQL being incredibly slow on Windows 2003 running IIS... on ASP/VBScript pages. PHP is also installed on the server and so is Microsoft SQL 2005 Express. (Yes, we're running ASP, PHP, MySQL and MS SQL on the same Windows 2003 Server using IIS.)
I was browsing the internet for a solution and saw a suggestion that I change output_buffering to on if MySQL was slow for PHP pages. Since we also served PHP pages with MySQL from the same server, it caught my eye. For the hell of it, I went into php.ini and changed output_buffering to on and suddenly MySQL and ASP was faster... MySQL and PHP was faster... Microsoft SQL Server 2005 Express and ASP was faster.... everything was faster... even stuff that had no PHP!
And I didn't even have to restart IIS. As soon as I saved the php.ini file with the change, everything got faster.
Apparently PHP and MySQL and IIS are so intertwined somehow that changing the buffering setting really effects the performance of the entire server.
So, if you are having performance problems on Windows 2003 & IIS, you might try setting output_buffering = On in php.ini if you happen to have PHP installed. Having it set to off apparently effects the performance of Windows 2003 and IIS severely... even for webpages that do not use PHP or MySQL.`
kamermans at teratechnologies dot net
21-Aug-2006 01:30
`Output buffering is set to '4096' instead of 'Off' or '0' by default in the php-5.0.4-10.5 RPM for Fedora Core release 4 (Stentz). This has cost me much time!`
webmaster [at] oltec-solutions [dot] nl
10-Jul-2006 06:00
`In re to erwinX at darwineX dot nl:
Adding an ampersand (&) before the hash seems to work too (for me at least), i.e.: http://somedomain.tld/blah.php?arg=x&#something
I guess php then interperts it as an argument to the script. Might save some time and resources.`
erwinX at darwineX dot nl
11-Nov-2005 05:35
`[Concerns IE refusing to jump to a #something in the URL.]
I encoutered a bug in IE6/W2000 that can be solved by turning output buffering on.
Maybe it also helps in other situations/M$-OS, not sure.
Situation:
A page with a hash in the URL, and IE doesn't jump to that location.
Example:
http://www.bla.com/test.php#something
- In test.php the anchortag is placed normally like:
<a name="something"><br></a>
- test.php takes a few seconds to load because of heavy-duty database activity.
IE just ignores the hash #something.
It looks like IE 'forgets' the hash if it hasn't encoutered it YET in the HTML.
Turning output buffering on resolves that issue.`
kend52 at verizon dot net
23-Jun-2005 11:25
`I ran out of memory, while output buffering and drawing text on imported images. Only the top portion of the 5MP image was displayed by the browser. Try increasing the memory limit in either the php.ini file( memory_limit = 16M; ) or in the .htaccess file( php_value memory_limit "16M" ). Also see function memory_get_usage() .`
gruik at libertysurf dot fr
10-Jul-2004 05:53
`For those who are looking for optimization, try using buffered output.
I noticed that an output function call (i.e echo()) is somehow time expensive. When using buffered output, only one output function call is made and it seems to be much faster.
Try this :
<?php
your_benchmark_start_function();
for ($i = 0; $i < 5000; $i++)
echo str_repeat ("your string blablabla bla bla", (rand() % 4) + 1)."<br>\n";
echo your_benchmark_end_function();
?>
And then :
<?php
your_benchmark_start_function();
ob_start ();
for ($i = 0; $i < 5000; $i++)
echo str_repeat ("your string blablabla bla bla", (rand() % 4) + 1)."<br>\n";
echo your_benchmark_end_function();
ob_end_flush ();
?>`
nobbie @t php d0t net
01-Apr-2004 04:49
`There is a problem in MSIE 5.5,6 with regards to Page compression. Users might experience pages not loading completely, or just a blank page.
This articles you are looking for is what you're looking for:
Microsoft Knowledge Base Article - 312496 (for MSIE 6)
Microsoft Knowledge Base Article - 313712 (for MSIE 5.5)
It states that you should upgrade to the latest MSIE Service Pack to fix the following problem:
Internet Explorer May Lose the First 2,048 Bytes of Data That Are Sent Back from a Web Server That Uses HTTP Compression`
tijmen
09-Jul-2003 04:44
`Trying to benchmark your server when using output_buffering ?
Don't forget that the value 4096 in the php.ini will give you complete different loadtimes compares to the value of 1.
In the first case the output will be sent after buffering 4096 and the loadtime timed at the end of the page will contain the loadtime needed to download the complete page in the clientbrowser while the second value will contain the loadtime needed to place the complete page in the buffer. The time needed for sending is not clocked.
This can be very frustrating if you don't see the differance between server and the 1st is using 4096 instead of 1.
Although technically much faster than the second server the second server was providing much better loadtime results.
This result will grow when using large amounts of output.
But this becomes interesting if you want to measure the time needed for the page to be loaded for the client.`
philip at thepr()jects dot ()rg
08-Feb-2001 11:17
`A few tutorials exist on this subject :
* http://www.zend.com/zend/art/buffering.php
* http://www.phpbuilder.com/columns/argerich20010125.php3`
add a note
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Last updated: Sat, 27 Jan 2007
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