PHP cURL error: Could not resolve proxy

Question

I'm trying to send a cURL request from a Windows Server 2008 machine using PHP (version 5.3.12) and keep receiving the error Could not resolve proxy: http=127.0.0.1; Host not found. As far as I cal tell, I'm not using a proxy - CURLOPT_PROXY is not set, I've run netsh winhttp show proxy to make sure there's not a system-wide setting in place, I've even checked all the browsers on my machine to confirm none are configured to use a proxy (just in case this could possibly have an effect). I'm having trouble figuring out why cURL insists on telling me that 1) I'm using a proxy and 2) it can't connect to it.

I'm able to resolve the error by explicitly disabling the use of a proxy via curl_setopt($curl, CURLOPT_PROXY, '');, but this isn't the greatest solution - a lot of the places I use cURL are in libraries, and it'd be a pain (not to mention less than maintainable) to go around and hack this line into all of them. I'd rather find the root cause and fix it there.

If it helps, this has happened to me only with POST requests so far. Command-line cURL (from a Git bash prompt) works fine. These calls also work fine from our dev machine, so it seems to be something specific to my machine.

If I need to apply the above hack, I will, but I thought before I resorted to that I'd ask the good folks of SO - is there anywhere I'm missing that could be configuring the use of a proxy? Let me know if there's any additional helpful info I forgot to add.

Solution

cURL relies on environment variables for proxy settings. You can set these on Windows via "Advanced System Settings".

The variables you need to set and/or change for optimum control are "http_proxy", "HTTPS_PROXY", "FTP_PROXY", "ALL_PROXY", and "NO_PROXY".

However, if you just want to avoid using a proxy at all, you can probably get away with creating the system variable http_proxy and setting it to localhost and then additionally creating the system variable NO_PROXY and setting it to *, which will tell cURL to avoid using a proxy for any connection.

In any case, be sure to restart any command windows to force recognition of the change in system environment variables.

[source - cURL Manual]