Notice: ob_end_flush(): failed to send buffer of zlib output compression (1) in

Question

I don't have any problem on localhost. but when i tested my codes on server, end of every page i see this notice.

my code:

<?php
ob_start();
include 'view.php';

$data = ob_get_contents();
ob_end_clean();
include 'master.php';
ob_end_flush();  // Problem is this line

Answer 1

I wouldn't recommend disabling the wp_ob_end_flush_all() function entirely, and I definitely wouldn't turn off zlib.output_compression in your php.ini file. Here's a better approach that replaces the source code causing the issue, and preserves the underlying functionality:

/**
 * Proper ob_end_flush() for all levels
 *
 * This replaces the WordPress `wp_ob_end_flush_all()` function
 * with a replacement that doesn't cause PHP notices.
 */
remove_action( 'shutdown', 'wp_ob_end_flush_all', 1 );
add_action( 'shutdown', function() {
   while ( @ob_end_flush() );
} );

More details on the cause, and why this is probably the best approach can be found here: Quick Fix for WordPress ob_end_flush() Error

Answer 2

WordPress attempts to flush the output buffers on shutdown. It fails because you have already called ob_end_flush().

You should be able to keep compression on, and simply unhook the flush action:

remove_action( 'shutdown', 'wp_ob_end_flush_all', 1 );

You can now call ob_end_flush() manually, and keep zlib compression on.

Answer 3

It solved when switched off zlib.output_compression in php.ini

zlib.output_compression = Off

Answer 4

You Should always disable front-facing errors on live sites for security reasons - regardless.

If you want to hide the errors in Wordpress and get a log of the errors for review instead, you can do something like the following in your wp-config.php file:

// Enable WP_DEBUG mode
define( 'WP_DEBUG', true );

// Enable Debug logging to the /wp-content/debug.log file
define( 'WP_DEBUG_LOG', true );

// Disable display of errors and warnings
define( 'WP_DEBUG_DISPLAY', false );
@ini_set( 'display_errors', 0 );

PS: If you want to use the remove_action code by alexg above, remove_action('shutdown', 'wp_ob_end_flush_all', 1); you will need to place it in the functions.php file of your theme.

PPS: You may also want to try using define(‘WP_MEMORY_LIMIT’,’1024M’); in your wp-config.php file - however, be careful that you don't allocate more than you need to as this affects the front end of Wordpress and you'll run the risk of running out of RAM if you have too many simultaneous hits on pages.

Answer 5

I found a particular plug-in was the cause on one of our client's WP sites.

In this case it was caused by the "NextGEN Gallery" plug-in, but weirdly simply deactivating and then activating the plug-in resolved the issue.

For anyone else having this problem it would be worth looking for suspect front end facing plug-ins and trying the same. If you find that the issue comes back when the culprit plug-in is reactivated you should file an issue with the plug-in author.

Answer 6

Simply Add this to theme functions.php file

remove_action( 'shutdown', 'wp_ob_end_flush_all', 1 );

Answer 7

One another scenario:

I was getting this notice on my live site but not on localhost and a staging / demo site, even though the demo site was on the same server as live site.

It turned out that zlib extension wasn't activated on live site and it was causing the notice. Once the zlib extension was activated, the notice stopped coming. So there was no code fix needed.

Answer 8

Just Use Your code on shutdown hook and make the position earlier And the default ob_end_flush() will recognize your output and will flush it

    add_action('shutdown', 'your_code', 0);
function your_code(){
/* Your Code Goes here */
}

Answer 9

Replace this ob_end_flush() replace with remove_action( 'shutdown', 'wp_ob_end_flush_all', 1 )

**
* Flush all output buffers for PHP 5.2.
*
* Make sure all output buffers are flushed before our singletons are destroyed.
*
* @since 2.2.0
*/
function wp_ob_end_flush_all() {
     $levels = ob_get_level();
     
     for ( $i = 0; $i < $levels; $i++ ) {
         ob_end_flush();
     }
}

The Updated code should look like this

function wp_ob_end_flush_all() {
    $levels = ob_get_level();

    for ( $i = 0; $i < $levels; $i++ ) {
        remove_action( 'shutdown', 'wp_ob_end_flush_all', 1 );
    }
}

Answer 10

I tried a brute-force approach which worked (I'm not satisfied with it, but hope this can help someone):

In the last line of the /wp-content/themes/<theme_directory>/functions.php (obviously before the php closure '?>') add the following line:

ob_get_clean();

Answer 11

This error can be caused by not having a closing ?> I came here after getting the error of "The plugin generated X characters of unexpected output during activation" and then activating debug. I narrowed down my include files in index.php to be the targetted file that worked with/without the error. Then I went into that file, and closed the file with the PHP tag, as there were a number of functions inside the file. Worked after that.

Answer 12

Don't be panic, it's so simple. just open function php and find this code

**
 * Flush all output buffers for PHP 5.2.
 *
 * Make sure all output buffers are flushed before our singletons are destroyed.
 *
 * @since 2.2.0
 */
function wp_ob_end_flush_all() {
  $levels = ob_get_level();
  for ( $i = 0; $i < $levels; $i++ ) {
    ob_end_flush();
  }
}

After you simply deleted "ob_end_flush();" and replace this code

remove_action( 'shutdown', 'wp_ob_end_flush_all', 1 );

solved it's 100%.

Answer 13

Try to disable wordpress debug mode and it's resolved. You can disable WP debug mode in /wp-config.php :

define('WP_DEBUG', FALSE);