Here's documented how a portable headless webserver could be made out of a Raspberry Pi. This guide has been made in case the setup needs to be redone, for whatever reason. It is written for Raspbian Jessie Lite, but should work for any Raspbian. Other ditros might need different commands and/or different file locations.
This guide describes how to set up a Raspberry Pi as a webserver (Apache with PHP and MariaDB/MySQL) which you can attach to any network without the need of a display (ever) nor a network cable. It also contains steps to set up a Samba share (to easily access the web server files from a work station), set up X11 (to get graphical interfaces on your workstation of applications running on the Pi) and make the Pi easily discoverable on the network by its hostname, including subdomains (to host multiple websites on the Pi).
The following hardware is assumed: