Build API's to accountancy packs/banks

We are a company providing factoring services (buying our customers outstanding invoices so they get their money faster). In order to facilitate the customers as much as possible we try and have API's ready so we can pull in their debtors, invoices and bankstatements. The API's for accountancy packs should be: - Build in PHP 7 - make use of a PDO database connection - should be in a class - contain a page on which our customer needs to enter his password and where the refresh token is then saved into a JSON file or into a tbl_api_login - retrieve all customers (the 7 critical fields will be provided) ==> dump in tbl_customer_data_import (database file will be provided) - retrieve all open invoices (7 critical and 12 optional fields will be provided) ==> dump in tbl_invoice_data_import (database file will be provided) - retrieve the invoice PDF's if available and store using naming convention [login to view URL] - retrieve bank statement files if available - should be able to call it from a cronjob so that a synch can be scheduled The API's for the banks to get the bankstatements / transaction overview should be: - should be in a class - contain a page on which our customer needs to enter his password and where the refresh token is then saved into a JSON file or into a tbl_api_login - should be able to indicate for how far back transactions should be loaded - able to extract all transactions and save it into tbl_bank_statement_import_before_load - use a PDO database connection We are willing to pay per API and are looking to link to the: - AFAS (accountancy) - UNIT4 (accountancy) - ABN-AMRO - ING - Rabobank - HSBC