How i can make category in this array?

How I can make category in this array? Please help me out how can make one key category then append documents?

Illuminate\Support\Collection Object ( [items:protected] => Array ( [0] => stdClass Object ( [id] => 19 [cust_id] => 206 [document_name] => Test [doc_file] => Vikas Singh.pdf [status] => [created_at] => [user_id] => 23 [document_category_id] => 8 [document_type_id] => 9 [para_1] => Kotak Mahindra Bank [para_2] => 08621000032676 [para_3] => PSIB000862 )

        [1] => stdClass Object
            (
                [id] => 20
                [cust_id] => 206
                [document_name] => test
                [doc_file] => Vikas Singh.pdf
                [status] => 
                [created_at] => 
                [user_id] => 23
                [document_category_id] => 9
                [document_type_id] => 
                [para_1] => 
                [para_2] => 
                [para_3] => 
            )

        [2] => stdClass Object
            (
                [id] => 22
                [cust_id] => 206
                [document_name] => GST1 Data 2
                [doc_file] => lodhi.doc
                [status] => 
                [created_at] => 
                [user_id] => 23
                [document_category_id] => 8
                [document_type_id] => 9
                [para_1] => Punjab and sind bank
                [para_2] => 08621000032676
                [para_3] => PSIB0000862
            )

    )

)

I have to make category in this array. I have category id . Please help me out

via Chebli Mohamed