Yii soap Internal Server Issue


I have a soap request to my central system, which is working fine in local, but when i upload it to online it is showing Internal Sever error. It seems connection got established and i could view all function in soap webserver using the function $client->__getFunctions(), but when i call a particular function it shows Internal server error.

$client = new SoapClient(Yii::app()->params->api_url.’/webservice/member/init’); ---------> working

$client->__getFunctions() -----> working, shows all functions

$infor = $client->checkLogin($username, $password, $campaign_id); ---------> [size="6"]not working[/size]

Please help me to solve this.