title: curl through proxy returns no content
body: <p>I'm working on a PHP script right now which sends requests to our school's servers to get real-time information about class sizes for different courses. The script runs perfectly fine when I don't use a proxy, returning a string full of course numbers and available seats. However, I want to make this a service for the students, and I'm afraid that if I make too many requests my ip will get blocked. So I'm attempting to do this through a proxy, with no success. As soon as I add the CURLOPT_HTTPPROXYTUNNEL and CURLOPT_PROXY fields to my requests nothing gets returned. I'm not even sure how to troubleshoot it at this point since I'm not getting an error message of any kind. Does anyone know what's going on or how to at least troubleshoot it?</p>
  
  <pre><code>$ch = curl_init();
  curl_setopt($ch, CURLOPT_URL, $url);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
  $proxy = explode(':', $proxy);
  curl_setopt($ch, CURLOPT_PROXY, $proxy[0]);
  curl_setopt($ch, CURLOPT_PROXYPORT, $proxy[1]);
  curl_setopt($ch, CURLOPT_HTTPPROXYTUNNEL, 1);
  curl_setopt($ch, CURLOPT_COOKIEFILE, 'tempcookie.txt');
  curl_setopt($ch, CURLOPT_COOKIEJAR, 'tempcookie.txt');
  curl_setopt($ch, CURLOPT_HEADER, 1);
  curl_setopt($ch, CURLOPT_REFERER, $ref);
  $exec = curl_exec($ch);
  
  echo curl_error($ch);
  print_r(curl_getinfo($ch));
  echo $exec;
  </code></pre>
  
  <p>Proxy used for tests: <code>75.147.173.215:8080</code></p>