json "autodecoded"

Hello,

for some strange reason, when I do a local test consisting of a POST of a json with curl , I just
receive a string containing the json

but when an external site tries to do the same, the POST variable I receive is an array with the json already decoded
only thing I know is that the external counterpart told me they wrote their site using scala

would there be any reason/special case where code igniter would auto decode the json string ?

thanks