What is output buffering

Question

What is output buffering and why is one using it in PHP

User · Answer

Output buffering is used by PHP to improve performance and to perform a few tricks.

You can have PHP store all output into a buffer and output all of it at once improving network performance.
You can access the buffer content without sending it back to browser in certain situations.

Consider this example:

<?php
    ob_start( );
    phpinfo( );
    $output = ob_get_clean( );
?>

The above example captures the output into a variable instead of sending it to the browser. output_buffering is turned off by default.

You can use output buffering in situations when you want to modify headers after sending content.

Consider this example:

<?php
    ob_start( );
    echo "Hello World";
    if ( $some_error )
    {
        header( "Location: error.php" );
        exit( 0 );
    }
?>

User · Answer

ob start        turns on output buffering  foo- gt bar        all output goes only to buffer ob clean        delete the contents of the buffer  but remains buffering active  foo- gt render       output goes to buffer ob flush       send buffer output  none   ob get contents        buffer content is now an empty string ob end clean        turn off output buffering   Buffers can be nested  so while one buffer is active  another ob start   activates a new buffer  So ob end flush   and ob flush   are not really sending the buffer to the output  but to the parent buffer  And only when there is no parent buffer  contents is sent to browser or terminal   Nicely explained here  https   phpfashion com everything-about-output-buffering-in-php

User · Answer

As name suggest here memory buffer used to manage how the output of script appears   Here is one very good tutorial for the topic

User · Answer

Output Buffering for Web Developers  a Beginner   s Guide   Without output buffering  the default   your HTML is sent to the browser in pieces as PHP processes through your script  With output buffering  your HTML is stored in a variable and sent to the browser as one piece at the end of your script  Advantages of output buffering for Web developers  Turning on output buffering alone decreases the amount of time it takes to download and render our HTML because it s not being sent to the browser in pieces as PHP processes the HTML  All the fancy stuff we can do with PHP strings  we can now do with our whole HTML page as one variable  If you ve ever encountered the message  quot Warning  Cannot modify header information - headers already sent by  output  quot  while setting cookies  you ll be happy to know that output buffering is your answer

User · Answer

UPDATE 2019  If you have dedicated server and SSD or better NVM  3 5GHZ  You shouldn t use buffering to make faster loaded website in 100ms-150ms   Becouse network is slowly than proccesing script in the 2019 with performance servers  severs memory disk  and with turn on APC PHP    To generated script sometimes need only 70ms another time is only network takes time  from 10ms up to 150ms from located user-server    so if you want be fast 150ms  buffering make slowl  becouse need extra collection buffer data it make extra cost  10 years ago when server make 1s script  it was usefull   Please becareful output buffering  have limit if you would like using jpg to loading it can flush automate and crash sending   Cheers   You can make fast river  or You can make safely tama

User · Answer

I know that this is an old question but I wanted to write my answer for visual learners  I couldn t find any diagrams explaining output buffering on the worldwide-web so I made a diagram myself in Windows mspaint exe    If output buffering is turned off  then echo will send data immediately to the Browser      If output buffering is turned on  then an echo will send data to the output buffer before sending it to the Browser      phpinfo  To see whether Output buffering is turned on   off please refer to phpinfo at the core section  The output buffering directive will tell you if Output buffering is on off     In this case the output buffering value is 4096 which means that the buffer size is 4 KB  It also means that Output buffering is turned on  on the Web server    php ini  It s possible to turn on off and change buffer size by changing the value of the output buffering directive  Just find it in php ini  change it to the setting of your choice  and restart the Web server  You can find a sample of my php ini below      Output buffering is a mechanism for controlling how much output data    excluding headers and cookies  PHP should keep internally before pushing that   data to the client  If your application s output exceeds this setting  PHP   will send that data in chunks of roughly the size you specify    Turning on this setting and managing its maximum buffer size can yield some   interesting side-effects depending on your application and web server    You may be able to send headers and cookies after you ve already sent output   through print or echo  You also may see performance benefits if your server is   emitting less packets due to buffered output versus PHP streaming the output   as it gets it  On production servers  4096 bytes is a good setting for performance   reasons    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   The directive output buffering is not the only configurable directive regarding Output buffering  You can find other configurable Output buffering directives here  http   php net manual en outcontrol configuration php  Example  ob get clean    Below you can see how to capture an echo and manipulate it before sending it to the browser       Turn on output buffering   ob start       echo  Hello World       save to output buffer   output   ob get clean        Get content from the output buffer  and discard the output buffer      output   strtoupper  output      manipulate the output    echo  output      send to output stream   Browser     OUTPUT    HELLO WORLD   Examples  Hackingwithphp com  More info about Output buffer with examples can be found here    http   www hackingwithphp com 13 0 0 output-buffering

User · Answer

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    http   php net manual en book outcontrol php  More Resources   Output Buffering With PHP

[php] What is output buffering?

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