Documentation Documentations Choose your solution SDK (Recommended) With the SDK it is super easy to get started. An all-in-one package with all web services in a single integration. Currently, only supported by PHP. API The APIs are supported by a diverse range of platforms and may be used to fit your special needs and to benefit specific web services in a more customized way. Custom The Custom Integration corresponds to the core layer and creates the opportunity to integrate Payer even for non-supported platforms and without any APIs.