If I understand what you’ve written (and I am no cURL/PHP expert, you’ve been warned 
), you are making the API call on the line $response = curl_exec($ch); but you then attempt to make the same call again but this time, you are feeding a URL through variables without the clientID - that is on this line $followAPI = json_decode(@file_get_contents(channelsApi . $channelName), true);
You should be able to alter that line to use the response from cURL: $followAPI = json_decode($response, true); - if that still doesn’t work, post what error you receive.
Worst case scenario, we should be able to do without the cURL and use: $followAPI = json_decode(@file_get_contents($channelsApi . $channelName . "?clientID=" . $clientId), true);
Also, as a note: @file_get_contents is blocked on some hosting servers for security reasons, but I can’t remember the alternative to it :banging head on desk: