Recently with the roblox group update, the API for changing a member rank has seemed to change. It may just be a simple error with the program itself or a change in roblox’s api. Here is the snippet that usually does it: $promote_user = curl_init("http://www.roblox.com/groups/api/change-member-rank?groupId=$group_id&newRoleSetId=$new_role_set_id&targetUserId=$target_user_id%22);
Edit: This post never got figured out. Instead I use Node.js and Noblox.js. You can search them up if you’re interested.
Can you tell what does the error message say? Is it a code 400 or 403 error? Also make sure you pass valid .ROBLOSECURITY cookie as the authorization.
By the way I would recommend you to use some lib which is able to do that kind of stuff. I don’t know about ones for php, but noblox.js is a great lib for node js which I use for stuff such as uploading models. It’s fairy simple to use it too.
If you are going to consider using it, I suggest you check out this reply under another thread which shows an example code for changing somebody’s rank in a group with the noblox.js lib.
That is how noblox changes a group rank. It appears to be the same as yours. Make sure you are passing the security token with it, as it is a required header.