$query = ee()->db->query('SELECT cat_url_title, cat_name, ch.channel_name  FROM exp_categories c
        LEFT JOIN exp_channels ch ON ch.cat_group = c.group_id
        WHERE c.cat_name LIKE "%'.ee()->db->escape_str($keywords).'%"');
foreach($query->result_array() as $row)
{
    echo $row['cat_name']."<br>";
}