Or, if you want to run the program in simple PHP on the same server where SuiteCRM is running, you have the basic Sugar Bean objects. That’s what I use for my bulk import script.
You can set things up as an entrypoint in your SuiteCRM so that your other system can invoke it from an URL.
Your best available reference for all this would be Jim Mackin’s eBook “SuiteCRM for Developers”, available for purchase online.