Please have a look at the result of phan for 3.x-dev, because there is a mismatch in what the methods are doing. The dump() method has an interface which declares the return type as stdclass, while in DataSet::dump() it is declared as array. At the same time the method DataObject::jsonSerialize() is defined to return a string, but currently returns the object from dump() instead. It looks like a json_encode() is missing here and that DataSet::dump() is defined wrong.
Please have a look at the result of phan for 3.x-dev, because there is a mismatch in what the methods are doing. The dump() method has an interface which declares the return type as stdclass, while in DataSet::dump() it is declared as array. At the same time the method DataObject::jsonSerialize() is defined to return a string, but currently returns the object from dump() instead. It looks like a json_encode() is missing here and that DataSet::dump() is defined wrong.