MySQL - Use group_concat function in another group_concat function

Alright i have this beautiful piece of code who help me obtain information about a fost like user name date posted comment etc, my problem is i want to extract 4 of last posts, i an obtain only one because i use a function, but with group_concat function i cand concat all 4 response in one large response converted in a json string. Here is my code:

begin
    declare ipost text;

    select concat('{"response":1,"posts":[',
        group_concat(
            '{',
            '"status":"',   data_comment.comment,'",',
            '"date":"',     data_datetime.time,'",',
            '"edited":"',   data_datetime.edited,'",',
            '"user":"',     concat(data_user_data.name,' ',data_user_data.lastname),'",',
            '"photo":', '{"', group_concat(data_photo.name separator '","'),'"}'
            '}'
        separator ',')
    ,']}') 
    into ipost
    from data_post
        inner join data_user_data on data_user_data.id = data_post.id_user
        inner join data_datetime on data_datetime.id = data_post.id_date
        inner join data_comment on data_comment.id = data_post.id_comment
        inner join fk_post__photo on fk_post__photo.id_post = data_post.id 
        inner join data_photo on data_photo.id = fk_post__photo.id_photo
    group by data_post.id
    desc
    limit 1;


    if(ipost is null) then
        return '{"response":0}';
    else
        return ipost;
    end if;
end

i get error: Invalid use of group function how to obtain array from this code:

'{',
    '"status":"',   data_comment.comment,'",',
    '"date":"',     data_datetime.time,'",',
    '"edited":"',   data_datetime.edited,'",',
    '"user":"',     concat(data_user_data.name,' ',data_user_data.lastname),'",',
    '"photo":', '{"', group_concat(data_photo.name separator '","'),'"}'
'}'

or if is possible to obtain 4 different rows with data from this function!