1st, I found CURLOPT_VERBOSE parameter. If you can not guess what is wrong with your CURL request, turn on CURLOPT_VERBOSE parameter. It’s very useful in such situation:
curl_setopt($ch, CURLOPT_VERBOSE, true);
Setting its value to TRUE forces CURL to output verbose information. It writes output to STDERR, or the file specified using CURLOPT_STDERR.
So I added parameter above and made step forward at once. I got the reason, why my CURL request didn’t work. CURL returned this information in the verbose mode: