How to Read and Write to a Textfile from Unity WebGL Parts 1-3

In this three part tutorial I will show you how to get around the issues in trying to write to a file from a Unity application when that application is built to WebGL. It will involve using PhP to work as an interface to take data from the WebGL app and write it to a file on the server. Reading data from the file and sending it back to the WebGL app will also be covered.