private static function appendExceptions($response, \Exception $e, $subtype = true)
 {
     if ($subtype === true) {
         if ($e instanceof MetadataProviderException) {
             $response .= "M";
         } elseif ($e instanceof NotificationException) {
             $response .= "N";
         } elseif ($e instanceof AccessException) {
             $response .= "A";
         } elseif ($e instanceof ItemsException) {
             $response .= "I";
         } elseif ($e instanceof SchemaException) {
             $response .= "S";
         } elseif ($e instanceof CreditsException) {
             if ($e instanceof ConflictingSessionException) {
                 $response .= "X";
             } else {
                 $response .= "C";
             }
         }
     }
     $response .= "|" . self::encodeString($e->getMessage());
     if ($subtype === true) {
         if ($e instanceof CreditsException) {
             $response .= "|" . $e->getCode() . "|" . self::encodeString($e->getClientUserMsg());
             if ($e instanceof ConflictingSessionException) {
                 $response .= "|" . self::encodeString($e->getConflictingSessionID());
             }
         }
     }
     return $response;
 }
 private static function appendExceptions($response, \Exception $e, $subtype = true)
 {
     if ($subtype === true) {
         if ($e instanceof DataProviderException) {
             $response .= "D";
         } elseif ($e instanceof SubscriptionException) {
             $response .= "U";
         } elseif ($e instanceof FailureException) {
             $response .= "F";
         }
     }
     $response .= "|" . self::encodeString($e->getMessage());
     if ($subtype === true) {
         if ($e instanceof CreditsException) {
             $response .= "|" . $e->getCode() . "|" . self::encodeString($e->getClientUserMsg());
             if ($e instanceof ConflictingSessionException) {
                 $response .= "|" . self::encodeString($e->getConflictingSessionID());
             }
         }
     }
     return $response;
 }