Just want to add that your proxy server most certainly need a user name and password. There are three parameters you need to set: http_proxy, http_proxy_user and http_proxy_pass.

You need to find out the proxy server used by your company. To find out the proxy server, check the proxy settings of your Internet Explorer.

If the proxy in your internet explorer is set to automatic, it means your network is using the WPAD (Windows Proxy Auto Discovery) protocol. Open the internet explorer, and type in: http://wpad/wpad.dat, which will download the proxy configuration script. Read the script to get the proxy server settings.