Im really new to php so sry for my small answer ? Im reading a book about it and what things this two are ? and what they do ?

Numbers_roman::tonumeral($year);

and

require_once("numbers/roman.php")

will be thankfull if a person answers this question

Hey,

Numbers_roman::tonumeral($year);
This looks like a namespace, however, I might be wrong. See: http://php.net/manual/en/language.namespaces.php
and

require_once("numbers/roman.php")
This this includes the file, but, instead of the "include" function which will only execute an error, this function will die if there is an error. By using the require_once, it will check to see if the file has already been included and if it has, not include it again.

Hope this helps :)