how to implement search in codeigniter

$_searchfield = $_REQUEST[‘key’]; $_searchfield = str_replace(“‘”, “”, $_searchfield); $query = $this->db->query(“SELECT * FROM td_product WHERE active=1 AND product_code like ‘$_searchfield’ UNION SELECT * FROM td_product WHERE active=1 AND product_title like ‘%$_searchfield%’ UNION SELECT * FROM td_product WHERE active=1 AND product_keyword like ‘%$_searchfield%’ UNION SELECT * FROM td_product WHERE active=1 AND product_desc like ‘%$_searchfield%’ limit 20”); … Read morehow to implement search in codeigniter