This may be not obvious, but if you specify the CURLOPT_POSTFIELDS and don't specify the CURLOPT_POST - it will still send POST, not GET (as you might think - since GET is default).
So the line:
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
is synonym to:
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
Even if you set the options like this (in this order):
curl_setopt($ch, CURLOPT_POST, 0);
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
it will send POST, since CURLOPT_POSTFIELDS is latter.
So if you want GET - make sure you don't have CURLOPT_POSTFIELDS specified somewhere.