i do believe you need to declare the function testfunc() BEFORE you try to reference it.  try that and see if it works.

I modified the code like this:

<?

function xyz() {

        echo "This always works";
}

class test {

        function testfunc() {

                echo "This now works";
        }

        function calltest() {

                $function_name = 'test::testfunc';

                $function_name();

        }
}

$t = new test;
$t->calltest();

?>

I got the exact same error.  I just don't think it can find functions inside a class.

Indirect reference was not supported in the :: operator.  I added support so that the method name can be indirectly referenced (e.g., foo::$bar()), but the kind of indirect reference you attempted is not supported.

I don't see this type of indirection being supported in the future, as it essentially requires invoking the compiler over again on the string (because you use an operator, ::, in your name expression).  If you really need this type of functionality, use eval() instead.