How to capture a php array and capture it in Java and transform it to Json

I mean, I'm using a PHP Web Service with NuSoap, the return of a method is an array (without converting it to a jsonstring)

Return structure

array('return' => 'tns:estructura')

Array to use

$data = array();

This array is then loaded with data and returned

return $data;

In java I can connect to the web service and invoke the method, what I do not know, is how to capture it (data type Object, ArrayList, etc), and then pass it to json

What I have is this

java.lang.Object result = _port.getMiMetodo("abc", num);

Another fact is that the query brings a lot of data, 1538 rows.