Memcache(d) to store PHP sessions

Edit: as of July 2014, there is a recent article discussing the use of php5-memcache instead of php5-memcache to store sessions on this blog. There are many posts around on the web about using memcached to store sessions data on high-availability servers, but few actually cover the whole topic and there are some elements that I thought might be of interest in the form of a quick recap. Memcached allows you to store frequently-used data in memory (RAM).

Quickly remove PHP 5.3 deprecated warnings in web applications

It's easy enough to do (although you shouldn't fix your issues that way, obviously), but I found it difficult to find information about it on the web. To change your PHP settings in order to avoid these warnings, one quick way is to edit your php.ini file (in /etc/php5/apache2/php.ini) and find the line that says
error_reporting = E_ALL
Possibly it will include other options.