Pasa los parametros con setOptions
Código PHP:
$wsdlOptions = array(
'login' => 'http_login',
'password' => 'http_password',
'proxy_host' => 'proxy.somehost.com',
'proxy_port' => 8080,
'proxy_login' => 'proxy_login',
'proxy_password' => 'proxy_password',
'local_cert' => dirname(__FILE__).'/_files/cert_file',
'passphrase' => 'some pass phrase');
$client->setOptions($wsdlOptions);