Mautic has API to interact with other systems. There is PHP API library for faster integration to PHP projects.
Install Mautic API library with Composer
API library isn't at Packagist in time of writing this article. Good chance is the library is at Packagist in time of reading, so install it from there and skip this.
Install from GitHub repo. So to use the library as Composer package from GitHub repo your composer.json should contain: