PHP数组去重..............过滤字段

1 $test_data = M('hot');  //实例化数据表
2 $data = $test_data->Distinct(true)->field('descriprion')->order('description desc')->select();  //利用distinct方法去重
3 $data = $test_data->group('department')->order('description desc')->select();  //利用group方法去重
4 dump($data);