What are the different ways data field/value mapping can be done in data integration/replication?

Goal-Trying to replicate data between two oncloud systems.Coding in Php

I am calling soap url of the source system and getting a xml as a output.Now the target system is also expecting a xml as input to insert data.I use xslt to convert the source data.Is there any other way I can do this convertion with payload as xml?Also what if both the system talk in json,and both expose REST url to communicate?What do I do in that case?