Argh! Impossible to use PHP shipping CGI?

[Christopher Wong]

Is it possible to use a PHP script for the shipping CGI? I don't know PERL,
but I know PHP. So I made an absurdly simple PHP script to test it out:

<?
print "status=pass\n";
print "option_count=1\n";
print "s1option=Method1\n";
print "s1price=12.34\n";
?>

This should work as per the API description, but I get an error message
saying "ShopSite detected that the information passed from the Custom
Shipping Add-on is incomplete and cannot be processed."

Running the script from the command-line produces this result:

status=pass
option_count=1
s1option=Method1
s1price=12.34

Where have I gone wrong? Is there something peculiar about PHP which makes
ShopSite refuse to use it?

[Christopher Wong]

By the way, is there any way to get more detailed error messages? I really
can't get anything out of this generic error message.