Something wrong with JSON when getting zabbix data

Question

I try to get data from zabbix with itemid, and when I get CPU value, them get normal, but when swap (for example) there is get back nothing, why?

curl -i -X POST -H 'Content-Type: application/json' -d '{"jsonrpc":"2.0","method":"history.get","params":{"itemids":[23311],"history":4,"output":"extend","time_from":"1413150714","time_till":"1413150774"},"auth":"1b7c445f0d3034082329e71e795f0604","id":1}' http://192.168.55.128/zabbix/api_jsonrpc.php

Answer 1

Could you post command output (curl -v = more verbose/talkative output):

curl -v -i -X POST -H 'Content-Type: application/json' -d '{"jsonrpc":"2.0","method":"history.get","params":{"itemids":[23311],"history":4,"output":"extend","time_from":"1413150714","time_till":"1413150774"},"auth":"1b7c445f0d3034082329e71e795f0604","id":1}' http://192.168.55.128/zabbix/api_jsonrpc.php