message: check http_client callback.
diff: @@ -1578,6 +1578,17 @@ static PHP_METHOD(swoole_http_client, on)
  return;
  }
  +#ifdef PHP_SWOOLE_CHECK_CALLBACK
  + char *func_name = NULL;
  + if (!sw_zend_is_callable(zcallback, 0, &func_name TSRMLS_CC))
  + {
  + swoole_php_fatal_error(E_ERROR, "Function '%s' is not callable", func_name);
  + efree(func_name);
  + return;
  + }
  + efree(func_name);
  +#endif
  +
  http_client_property *hcc = swoole_get_property(getThis(), 0);
  if (strncasecmp("error", cb_name, cb_name_len) == 0)
  {
  