send / ping another server from nginx

I need the following configuration:
when the nginx is getting a request I need to do 3 things:
1. write a log entry
2. reply with a pixel gif file
3. in some instances I need to ping a different url like this: GET http://another_domain.com?a=1&b=2

number 3 is on top of the other two, so a reply with a gif is a must. I do not need to wait for a reply from another_domain.com this can be sent and forget...

At the moment I do it using php, but it takes to long and I want a way to do it directly from nginx.

Thanks