The E*TRADE PHP SDK by E*TRADE allows developers to access the E*TRADE trading platform from their PHP applications. The SDK includes libraries for handling authentication, accounts, market data, and orders.
The financial trading sector has witnessed a number of APIs appear on the trading scene over the past few years, like with TradeKing, Data Explorers, etc..
ZenPayroll, a cloud-based payroll provider, has unveiled an API that a dozen partners, including Expensify and Maxwell Health, have already integrated with.
G2 Web Services has launched an API that helps banks evaluate the risk associated with merchants and originators of Automated Clearing House (ACH) transfers.