drupal_http_request assumes presence of Reason-Phrase in Status-Line

This patch pads the array to length 3 before putting it into the three variables.

I understand what you mean, but I'm not sure how to do this elegantly.

The problem goes beyond simply making sure the code is notice-free; it's also about sanitizing the response. Since the function is a pretty complete implementation of an HTTP client, it should deal with the possibility that the server response violates the protocol, preferably without crashing and burning.

For now, this is the best I can come up with. It assumes that the required fields are present, but not the optional field - if the server really messes up for whatever reason, the code will trigger notices:

  // Status line consists of HTTP version, 3-digit response code and optional message.
  $status_line = explode(' ', trim(array_shift($split)), 3);
  list($protocol, $status) = $status_line;
  $text = count($status_line) > 2 ? $status_line[2] : '';

The comment would go a good way to making the code understandable there.

(The alternative is to make a really strict regular expression - /^(HTTP\/[0-9]+\.[0-9]+) ([0-9]{3,3})( (.*))?$/ and break the connection on a mis-match. I don't like expressions unless they're needed.)