On the SitePoint PHP blog they've posted an article from author Joel Degan showing you how to create a bot to auto-trade cryptocurrency with a bit of PHP and this boilerplate code.

This tutorial will walk you through the full process of building a bitcoin bot with PHP – from setup, on to your first execution of an automated trade, and beyond.

[...] But, you say, I am a coder who likes to automate things, surely we can fire up some BTCbot and we can have it just do the work for us, it will make us millions in our sleep, right? Probably not. I don’t want to write a bot and publish it with a single strategy and just say “here, use this”, I don’t think that is helpful to anyone, I would rather give you the tools and show you how to write strategies yourself, show you how to set up data collection for the strategies and how to implement them in a trading system and see the results.

He then walks you through the installation of the boilerplate code and the list of commands/scripts that come with it. He shows how to set up the Redis/MySQL connections and each of the sites you'll need to set up an account on to either perform trades or get the latest currency information. With all of that installed and set up he starts in on the code and functionality, grab the latest data, write a bit of code to manipulate that data and create other handling to manage your own preferences and trading rules.