add agent to curl request php code example

Example: user-agent cURL php

$config['useragent'] = 'Mozilla/5.0 (Windows NT 6.2; WOW64; rv:17.0) Gecko/20100101 Firefox/17.0';

curl_setopt($curl, CURLOPT_USERAGENT, $config['useragent']);
curl_setopt($curl, CURLOPT_REFERER, 'https://www.domain.com/');