There are two kinds of language construct in php for including file.
include and require
There is basic difference in both of them is how handle they errors and script execution.
Using "include" - will give warning in case file is not present in path or not permission to read and php script will continue .
Using "require" - will halt the system and stop execution in case file is not present in path or not permission to read.
and their sister method include_once "dir/filepath/filename.ext"
and require_once "dir/filepath/filename.ext"
include_once and require_once is best at point - when you are including multiple file and not remember any file is already including or not then _once will remember if file is included already then it skip for duplicate include.
If your including file is not so important to include in page then you can go with "include" or include_once
or in other case your including file is most important to process further page process then do use
require or require_once
If still you feel difficulty to implement, just mail me
i will do free for you.