PinPoint Attributes using API

I am trying to send an email using a template in PinPoint that I have created. When I attempt to set substitutions or attributes in the API call using PHP nothing happens. It will always resort to the default values for the attributes. I have combed through the documentation on customization and I seem to be missing something as I cannot seem to get it to work at all. Any suggestions/code example would be greatly appreciated as the documentation does not provide any on customization.