That version_compare() doesn't do anything, PHP4 doesn't under stand `public` nor `static` methods
include/require[_once] is language construct, not function.
That driver mechanism doesn't allow user based drivers.
driver.iface.php seems to be mandatory and therefor should use require, not include
I don't like these extension_loaded() checks
I'd like to be able to set $wsdl from the constructor
There are quite few lines waaaay longer then 80chars
Tabs used, not spaces