how can i get param from "{"attachments[1][item_name]","1"}"

[Caiyun Deng]

Module: xyadmin_email_controller, Line: 22, 

My print's "Req : post_params ( )" is [{"title","asdfasdf"},

                                       {"serverlists[]","3"},

                                       {"users",[]},

                                       {"content","sdfasdfasdf"},

                                       {"attachments[0][item_type]","1"},

                                       {"attachments[0][item_id]","1"},

                                       {"attachments[0][item_name]","1"},

                                       {"attachments[0][item_amount]","1"},

                                       {"attachments[1][item_type]","2"},

                                       {"attachments[1][item_id]","1"},

                                       {"attachments[1][item_name]","1"},

                                       {"attachments[1][item_amount]","1"}]

******

I tried:

Req:post_param("attachments") -->undefined

Req:param_group("attachments[]") -->[]

Req:deep_post_param("attachments") --> will raise error,

So, how do i get the attachments?