Unable to make external HTTP Requests using PHP cURL behind Proxy - php

Question

I'm running a local LAMP web server inside a virtualbox VM configured through vagrant which is sitting behind a corporate proxy.
From the web server I'm trying to make external HTTP requests using php-curl but they're simply timing out; However requesting local addresses via php-curl works fine.
Snippet:
$ch = curl_init();
$fp = fopen('/tmp/curl-debug.txt', 'w');
$options = array(
CURLOPT_URL => 'http://stackoverflow.com',
CURLOPT_RETURNTRANSFER => true,
CURLOPT_HEADER => true,
CURLOPT_FOLLOWLOCATION => true,
CURLOPT_AUTOREFERER => true,
CURLOPT_CONNECTTIMEOUT => 10,
CURLOPT_TIMEOUT => 15,
CURLOPT_MAXREDIRS => 10,
CURLOPT_VERBOSE => true,
CURLOPT_STDERR => $fp
);
curl_setopt_array( $ch, $options );
$response = curl_exec($ch);
curl_close($ch);
Debug log:
* Hostname was NOT found in DNS cache
* Trying 23.201.173.230...
* Connection timed out after 10001 milliseconds
* Closing connection 0
Helpful info:
My OS: Windows 7
VM OS: Ubuntu 14.04.4
PHP v5.5.9-1
Apache 2.4.7
VM has a private_network ip of 192.168.33.10
It's worth mentioning I'm behind a corporate proxy which the vm is configured to play nicely with AFAIK.
If I try running curl from the command line of the virtual machine, everything works as expected
E.g: curl http://stackoverflow.com/ returns html.
nslookup from inside VM:
Server: 10.0.2.3
Address: 10.0.2.3#53
Non-authoritative answer:
Name: stackoverflow.com
Address: 104.16.35.249
Name: stackoverflow.com
Address: 104.16.34.249
Name: stackoverflow.com
Address: 104.16.37.249
Name: stackoverflow.com
Address: 104.16.33.249
Name: stackoverflow.com
Address: 104.16.36.249
I've read around that /etc/resolv.conf could play a role in this and have made sure that the user group www-data has read access to it. My resolv.conf:
nameserver 10.0.2.3
search proxy.internal
I've tried changing the nameserver to 8.8.8.8 no luck and tried changing search to the ip that proxy.internal resolves to.
I've also tried reaching the IP which the domains resolve to via php-curl to bypass the dns but it still timesout.
I'm out of ideas, and google results!

Answer 1

My first thought is to make sure the php-curl extension is installed properly and working, by using grep on your apache php.ini. I realize your question states you have php-curl working on local addresses, but no further details were provided so I would be inclined to double check.
My next thought is that the corporate proxy is interfering - try booting the box on a different internet connection (your house, tethered to your phone, whatever) and see if that solves your problem. If it doesn't at least you can rule out the proxy as being the immediate issue.

Answer 2

The problem was the proxy server.
I falsely assumed that because my virtual machine was configured to play nicely with the proxy, all Apache requests would go via the VM.
Solution - tell php-curl about the proxy:
curl_setopt($ch, CURLOPT_HTTPPROXYTUNNEL, true);
curl_setopt($ch, CURLOPT_PROXYPORT, $PORT);
curl_setopt($ch, CURLOPT_PROXY, $PROXY_ADDR);
curl_setopt($ch, CURLOPT_PROXYUSERPWD, 'username_here:password_here');