RetroPie Web GUI is a web application for managing your RetroPie roms and seeing your system information on-the-fly. I made this application to make managing your roms easier.
To get started it is best to follow the README.md file provided with the application. This will have the latest setup instructions. Basicly you install apache (sudo apt-get install apache2) and PHP (sudo apt-get install php5 libapache2-mod-php5 php5-mcrypt). Once apache is installed cd to the html directory (cd /var/www/html/), clone the git repository (git clone https://github.com/gwhitcher/RetroPie-Web-GUI.git), and finally setup a symbolic link to your roms directory (ln -s /home/USERNAME/RetroPie/roms /var/www/home/RetroPie-Web-GUI/roms (replace USERNAME with your system username)). You may have to fix permissions on your html directory so you can write to it.
Because apache starts with linux, a web application is a great way to manage your roms. By default it is setup locally. This means you can only access it while on the machine RetroPie is installed on. This isn't ideal of course. So you will want to setup the application with your hostname. You can find this by typing "hostname" into the terminal. You will want to go into your system-config.php and update the BASE_URL by replacing localhost with your hostname. You will then be able to access the RetroPie Web GUI anywhere on your network. You can now easily add and remove roms. Additionally you can add a .htpasswd file for security.