OK, it looks like I've got it. Here is the gist of the solution, which
pretty much follows the Walsh article and this article:
http://upshots.org/php/transacting-with-authorize-net-via-php-and-curl.
Thanks for the help. $params = array(); //filled wi...
I've been struggling with this as well. When I pass the parameters as an
array via cURL to https://test.authorize.net/gateway/transact.dll, I get
a "merchant login id or password invalid" error. However, if I switch it
back to sending a url encoded s...