This is a fascinating project.  I'm building a passive SOAP server on the same Linux machine that hosts the CRM, to integrate QB desktop software company data into the CRM!  Using PHP 7, MySQL.  

Wordpress plugin to allow website visitors to schedule appointments to view luxury apartments using RentCafe API.

Pulling complex HR data from BambooHR using their REST API, storing it in a database, mapping fields and performing nightly batch updates via cron job into Deputy system for company with multiple locations and numerous part time employees with high turnover and flexible schedules.  Batch Report grid view with filters.  Databasing ALL request/response activity from APIs as is best practice.

A PHP-based system using Bandwidth Port Out Validation API to allow telecom company to require certain information from customers seeking to submit port out requests, to ensure against fraud and bulk port outs.  Designed database to hold request/response and customer status data from system, to integrate with client's existing data.