<?php
class API_Client {
       private static $instance = NULL;
       private function __construct() {
       }
 /**     * Return client instance or create initial
  *
  * @todo save session id or set var or something so each soap call doesn't need to auth
  * @return object
  * @access public
  */
  public static function getInstance() {
     if (!self::$instance) {
        echo "Eccomi qua";
        $ns   = "auth";
        $wsdl = "https://pi731.dncsrl.com/sap/bc/soap/wsdl?services=RFC_SYSTEM_INFO";
        //Create our Auth Object to pass to the SOAP service with our values
        echo "Sto inserendo i parametri di autenticazione";
        $auth->username = 'j2ee_admin';
        $auth->password = 'abcd1234!';
        $auth_vals    = new SoapVar($auth, SOAP_ENC_OBJECT);
        //The 2nd variable, 'authenticate' is a method that exists inside of the SOAP service (you must create it, see next example)
        $authenticate = new SoapHeader($ns,'authenticate',$auth_vals, false);
        $client = new SoapClient($wsdl,array('cache_wsdl' => 0));
        $client->__setSoapHeaders(array($authenticate));
        self::$instance = $client;
        echo "sto per eseguire la chiamata";
     }
     return self::$instance;
  }


  private function __clone(){
  }
}   //These are a few sample calls to functions inside of the WSDL

try {
        echo "Eseguo la chiamata";
        $data_1 = API_Client::getInstance();
        echo "Stampo il risultato";
        echo $data_1;
}catch (Exception $e){
        echo $e->getMessage();
}

?>