Programmatically create Template Variables?

I have a task where I need to be able to programmatically create template variables on the fly. Looking through the documentation I cannot find how I could, with just PHP, create a template variable.

Does anyone have a simple code snippet they could share that can do this?

Do you want to create a new TV, or assign a value for a given resource to an existing TV?

http://rtfm.modx.com/revolution/2.x/making-sites-with-modx/customizing-content/template-variables/accessing-template-variable-values-via-the-api

I am actually trying to create the actual template variable. I am able to add the value myself through the code you linked but the actual creation was the issue I was looking for.

I think I found a solution on here http://bobsguides.com/revolution-objects.html

Trying that out now but it looks promising.