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public function get_contents()

    {

        $param = $_POST["param"];

        $this->output($this->Madmin->get_contents($param));

    }

public function get_contents($param)

    {

        $category_id_list = isset($param["category_id_list"]) ? $param["category_id_list"] : [];

        if (empty($category_id_list)) {

            $result["count"] = 0;

            $result["list"] = [];

            return $result;

        }

        

        $this->db->start_cache();

        $cname=[];

        $cname["c_1"] = "1";

        $cname["c_2"] = "2";

        $cname["c_3"] = "3";

        $cname["c_4"] = "4";

        $sql = "(";

        $bFirst = true;

        foreach($category_id_list as $tablename){

            $s = "select A.create_time as create_time, A.user_id user_id, '{$tablename}' as category_id, B.nickname user_nickname, '{$cname[$tablename]}' as category_name";

            $s .= " from " . $tablename . " A";        

            $s .= " left join user B on A.user_id = B.id";

            if (!empty($param["keyword"]))

                $s .= " where B.nickname like '%{$param["keyword"]}%'";

            $s .= " group by A.user_id";

            if(!$bFirst){

                $sql .= " UNION ALL ";

            }

            $bFirst = false;

            $sql .= "(" . $s . ")";

        }

        $sql .= ") as calc";

        $this->db->select("*");

        $this->db->from($sql);

        

        $this->db->stop_cache();

        $result = [];

        $result["count"] = $this->db->count_all_results();

        $this->db->order_by("create_time", "asc");

        $this->db->limit($param["itemsByPage"], ($param["page"] - 1) * $param["itemsByPage"]);

        $result["list"] = $this->db->get()->result_array();

        $this->db->flush_cache();

        return $result;

    }