user_agent.php
public function useProxy($proxy, $username, $password)
    {
        if (! $proxy) {
            $this->proxy = false;

            return;
        }
        if ((strncmp($proxy, 'http://', 7) != 0) && (strncmp($proxy, 'https://', 8) != 0)) {
            $proxy = 'http://' . $proxy;
        }
        $this->proxy          = new SimpleUrl($proxy);
        $this->proxy_username = $username;
        $this->proxy_password = $password;
    }
public function useProxy($proxy, $username, $password)
    {
        if (! $proxy) {
            $this->proxy = false;

            return;
        }
        if ((strncmp($proxy, 'http://', 7) != 0) && (strncmp($proxy, 'https://', 8) != 0)) {
            $proxy = 'http://' . $proxy;
        }
        $this->proxy          = new SimpleUrl($proxy);
        $this->proxy_username = $username;
        $this->proxy_password = $password;
    }
Sets proxy to use on all requests for when testing from behind a firewall.
Set URL to false to disable.

@param string $proxy        Proxy URL.
@param string $username     Proxy username for authentication.
@param string $password     Proxy password for authentication.