richard

$added_api_key = False;
    if ($headerParams != null) {
      foreach ($headerParams as $key => $val) {

    // La linea de abajo la agregue yo Richard y comente la anterior
    //$headers[] = "$key: $val";
        $headers[$key] = $val;

        if ($key == $this->headerName) {
          $added_api_key = True;
        }
      }
    }

...

if (strpos($headers['Content-Type'], "multipart/form-data") < 0 and (is_object($postData) or is_array($postData))) {
      $postData = json_encode($this->sanitizeForSerialization($postData));
    }