resource get trailer bindings

$paramsTrailers =  array("resourceId"=>xxxxxxxx,"unitId"=>0,"trailerId"=>0,
                        "timeFrom"=>strtotime('2015-12-23 00:00:00'),"timeTo"=>strtotime('2015-12-23 23:59:59'));
$trailers = $wialon_api->resource_get_trailer_bindings(json_encode($paramsTrailers));

I want to get the trailers, but I get the error 7

I thank your help