How to consume this soapclient webservice in php?

Question

How to consume this soapclient webservice in php ??? tried the code below and gave the following error.

Code

$client = new SoapClient('http://www.smsviaweb.com.br/SMSVIAWEB.asmx?wsdl');
  $params = array('Login'    => 'xxxxx', 'Senha'    => 'xxxxx','Telefone'=>'xxxxx', 'Mensagem'=>'xxxxx');
  $client->__soapCall("Envia", $params);

Error

Fatal error: Uncaught Soapfault Exception: [Soap:Server] System.Web.Services.Protocols.Soapexception: Server was Unable to process request. ---> System.Nullreferenceexception: Object Reference not set to an instance of an Object. at SMSVIAWEB.Sends(Objmsgsmsvw Objmsg) --- End of Inner Exception stack trace ---

getFunctions

 array(6) {
  [0]=>
  string(38) "EnviaResponse Envia(Envia $parameters)"
  [1]=>
  string(50) "EnviaLoteResponse EnviaLote(EnviaLote $parameters)"
  [2]=>
  string(62) "ExecutaImportResponse ExecutaImport(ExecutaImport $parameters)"
  [3]=>
  string(38) "EnviaResponse Envia(Envia $parameters)"
  [4]=>
  string(50) "EnviaLoteResponse EnviaLote(EnviaLote $parameters)"
  [5]=>
  string(62) "ExecutaImportResponse ExecutaImport(ExecutaImport $parameters)"
}
array(9) {
  [0]=>
  string(37) "struct Envia {
 OBJMsgSMSVW OBJMsg;
}"
  [1]=>
  string(127) "struct OBJMsgSMSVW {
 string Login;
 string Senha;
 string IDCliente;
 string Telefone;
 string Mensagem;
 string DataAgenda;
}"