Just to save anyone getting caught out with out of date information, if you want to install phpsysinfo on your Raspberry Pi 2 or 3 running Jessie… the picture below is self-explanatory – simple to install and some worthwhile info. RPI-Monitor is another useful monitoring tool.
sudo apt-get update && sudo apt-get upgrade (if not done recently)
sudo apt-get install -y apache2 php5 libapache2-mod-php5 (if not already done)
sudo apt-get install -y phpsysinfo
sudo ln -s /usr/share/phpsysinfo /var/www/html
Then enter into your browser:
and you get something like this rather nice display