Fix W3 Total Cache W3_Plugin_TotalCache::ob_callback() expected to be a reference

Around a year ago I was playing with W3 Total Cache plugin on HHVM while I got an annoying warning

Warning: Parameter 1 to W3_Plugin_TotalCache::ob_callback() expected to be a reference, value given in /wp-includes/functions.php on line 3269

The funny part is that one of the functions was passing by reference which I still could not find the reason for it, maybe it was a limitation in PHP 4.3. Removing one character “&” fixed the issue so I submitted a pull request to the author although the repository currently does not accept pull request. Later on as PHP 7.0 was released, the issue started to show on PHP as well which brought more attention to this small fix. The users comments included anger such as user @kmob2 who said

this is becoming a running gag

Even more user @pratham2003 proposed a one line bash command to solve the problem

sed -i.bak 's/function ob_callback(&/function ob_callback(/g' /path/to/public_html/wp-content/plugins/w3-total-cache/lib/W3/Plugin/TotalCache.php

I hope that the developers will finally listen to the users and fix it soon!

Install Sphinx 2.0.4 on CentOS 6.2

– Make sure to check CentOS, PHP-FPM, Nginx, memcached and MYSQL posts.

– Get fresh RPM from

– Install Sphinx

rpm -Uhv

– Create sample MySQL database

Compress your HTML, CSS and Javascript using simple PHP Code

Although Compression is a very important method of making your pages lighter and easier for users to download, it’s definitely going to cost you more CPU and on high load servers it’s not recommended unless you already know how to cache your HTML pages.