EDIT: /sigh -- that was easy. I'll leave here in case someone else is in the same boat.
I was one...
echo "The current PHP version being used is: " . phpversion ();
... away from seeing:
"The current PHP version being used is: 4.4.9"
Req of 5.2 here: http://developer.authorize.net/downloads/
In my case (1and1), you can create an .htaccess file in the site's root folder with the following line:
AddType x-mapp-php5 .php
Voila.
I've written a site that worked on my local box, then worked perfectly with a return page on my own business website. But now that I've moved it to the client's server, it's busted.
I'm now testing with a file that only has this line in it:
06-04-2011 10:20 PM - edited 06-04-2011 10:27 PM