>Do you think that this may be due to me using an older version of PHP on the Windows server?
I doubt it.
You'll need to examine the php file that makes your certificate for display.
I suspect php is trying make a either a pdf or a Word document for your certificate. PHP can't build either without an extra framework library.
If so, the library is
probably installed in the php/include folder on your linux box. You'll need to copy it to your Windows box.
To try to find the include folder, you can get php to reveal all about itself.
Put this text in a file called phpinfo.php in the webroot
<?php
phpinfo();
?>
Then call it with
http://localhost/phpinfo.php
You will get a display of ALL the data php has about itself.
One item is 'include_path'
My Windows shows this
include_path .;c:\Program Files\php\includes
It means that include looks first in the current folder (.)
then if the file hasn't been found look in c:\Program Files\php\includes
My unix shows this
include_path .:/usr/local/php/lib/php
It means that include looks first in the current folder (.)
then if the file hasn't been found look in /usr/local/php/lib/php
So my PDF framework and MSWord framework are in c:\Program Files\php\includes and /usr/local/php/lib/php respectively.
Remove the phpinfo.php file when you are finished. It is a security hole.
Good luck,
Barry.