API Key for hubspot interface between hubspot and service m8 (native software)

the current thrid party addon (zapier) has limited API intergration betwen hubspot and service m8. We are now using hubspot as part of our business but now need to build an API interface using PHP developers, we have been advised by our developers that they require a Service M8 API Key in order to intergrate the two CRM's together. Can i get or can they get access to the API key to build the intergration we need, or the alternative is we use a direct hubspot partner CRM system that has the inface in mind. Can you Assist?