This method allows to retrieve the version of the Zabbix API.
This method is available to unauthenticated users and must be called without the
auth parameter in the JSON-RPC request.
(array) The method accepts an empty array.
(string) Returns the version of the Zabbix API.
Starting from Zabbix 2.0.4 the version of the API matches the version of Zabbix.
Retrieve the version of the Zabbix API.
CAPIInfo::version() in frontends/php/include/classes/api/services/CAPIInfo.php.