fetchByMerchantTransactionId method returns a Transaction object whose merchantTransactionId value matches the input. This ID could be assigned by you (for example, when you conduct a one-time transaction) or by Subscribe while generating a rebilling transaction for an active AutoBill object.
Because Transactions change their status as they go through their life cycle in Subscribe, returned Transaction objects might show a different status each time they are returned, especially for Subscribe-processed transactions. The latest Transaction status is the first entry in the statusLog array (see the statusLog attribute in Transaction Data Members. For example, if you create a one-time transaction and call authCapture() on it, the latest transaction status is Authorized. Later, if you retrieve the same Transaction by its ID with this method, the latest status could be Captured.
Input
srd: sparse response description, a SOAP string (which must be a JSON object), in which you specify the elements you want returned.This parameter enables the calling system to constrain amethod call to return only components you specify. This gives you greater control over returned content, and improves response time within the Vindicia platform by reducing the processing needed for the call.
Some fields are required, either practically or in the WSDL, and will be returned regardless of the srd. A null srd returns the complete response.
merchantTransactionId: the merchantTransactionId value, which serves as the search criterion.
Output
return: an object of typeReturn that indicates the success or failure of the call.
transaction: the Transaction object whose merchantTransactionId value matches the input.

