help using php to communicate with outside websites that use POST

i have a website that a user must enter a VIN number and select an axle ratio and it searches for matching tire calibrations in a text file. However, there is another website you have to goto first to get the axle ratio.

I want my site to automatically get the axle ratio from the other website based on the VIN. The other website prompts you for the VIN number also and then displays the axle ratio on the next page. However, this site does not use the GET method. I assume they use the POST method so there is no way to pass the information through the URL.

Is there anyway I can pass the VIN number entered in my website to the other site to be analyzed? Maybe I could link it directly to the submit the number to their ACTION file. Is this possible?

You should be able to look at the source for the page and get the variable that is being passed then use that in a URL in the same form as you would a GET request.