ZF-12143: Built in JSON encoder ignores NULL values when encoding objects.
In the built in JSON encoder method _encodeObject() the property is ignored if the value is not set. This means that all properties which have NULL as value are not included in the JSON output.
If the built in encoder really behaves exactly the same as json_encode (like the documentation states) it would include all properties also the ones that have NULL as a value. Optionally an ignoreNullValues option could be added instead.