I wanted to upgrade this server's PHP to 5.4. According to what I read from Blite official website, running Blite on 5.4 would reduce again my memory usage from 810kB to less than 350kB. But the stable version when I try to upgrade via
apt-get install php5 is PHP 5.3.21.
So I tried adding dotdeb repository to my
sources.list, then made an apt-get update and apt-get install php5. But the last command,
apt-get install php5 removed the package roundcube-sqlite, which was my choice of SQL backend for webmail on this server. At first, I didn't notice the warning about "The following package will be removed", and I made roundcube unusable on the server. PHP 5.4 was successfully installed though. Anything I tried to install roundcube-sqlite failed.
During this time, I could test the performance of Blite, but, unfortunately, I didn't see any change in memory peak usage, I didn't even get the memory usage going below 800kB. In my point of view, there was absolutely no change, no benefit.
I then removed dotdeb from my sources.list, removed php5, and make an
apt-get update; apt-get install roundcube to reinstall roundcube, along with PHP 5.3. This made my server go back to its previous state.
This experience made me think that to successfully use latest versions of softwares, the best way to do is compile from source. Having broken dependencies on my packages will be the worst thing I don't need for my servers.