API to talk between mySQL and Progress/SX database - MSSQL 2005

we are building an ecommerce site for our client using PHP/mySQL. front end of site is being hosted on 3rd party server and linked to an in-house server. the inhouse server holds an MSSQL 2005 dB that is run using Progress/SX on IBM WebSphere - this is the inventory dB. we need an API written to talk between mySQL (for the ecommerce site) and the Progress/SX (MSSQL 2005) dB (on-site inventory system).