Alter Caching & API-Communication in existing PHP Web-App

I have a 90% finished Web-Application for which is need three alterations: - After User-Input, our Web-App requests an public available API. I need an option to contact the API with an alternative parameter. - We Cache the results file-based. The new results with the alternativ parameter should be cached in their own directory. - The public available API only gives us 200 results. Sometimes we need more. So i need a way we can communicate 500+ requests to the api and cache the results. - Implement 404-Page in non-valid Short-URL (we use short urls) are requested