PHP Cookbook

8.12. Buffering Output to the Browser

Problem

You want to start generating output before you’re finished sending headers or cookies.

Solution

Call ob_start( ) at the top of your page and ob_end_flush( ) at the bottom. You can then intermix commands that generate output and commands that send headers. The output won’t be sent until ob_end_flush( ) is called:

<?php ob_start(); ?>

I haven't decided if I want to send a cookie yet.

<?php setcookie('heron','great blue'); ?>

Yes, sending that cookie was the right decision.

<?php ob_end_flush(); ?>

Discussion

You can pass ob_start( ) the name of a callback function to process the output buffer with that function. This is useful for postprocessing all the content in a page, such as hiding email addresses from address-harvesting robots:

<?php 
function mangle_email($s) {
    return preg_replace('/([^@\s]+)@([-a-z0-9]+\.)+[a-z]{2,}/is',
                        '<$1@...>',
                        $s);
}

ob_start('mangle_email'); 
?>

I would not like spam sent to [e-mail]!

<?php ob_end_flush(); ?>

The mangle_email( ) function transforms the output to:

I would not like spam sent to <ronald@...>!

The output_buffering configuration directive turns output buffering on for all pages:

output_buffering = On

Similarly, output_handler sets an output buffer processing callback to be used on all pages:

output_handler=mangle_email

Setting an output_handler automatically sets output_buffering to on.

See Also

Recipe 10.11 uses output buffering in a database error logging function; documentation on ...