$match = "/^\d{4}-\d{2}-\d{2} [0-2][0-3]:[0-5][0-9]:[0-5][0-9]$/";

        $s = $this->input->post("report_start"). " " . $this->input->post("report_start_time").":00";
        $e = $this->input->post("report_end"). " " . $this->input->post("report_end_time").":59";

        if($this->input->post("action") != "")
        {
            echo trim($s). " => " . preg_match($match, trim($s));
            echo "<br>";
            echo trim($e). " => " . preg_match($match, trim($e));
        }