Non-ASCII is mostly an issue on localized servers, yes, but theoretically you can run into the same issues on English servers. It also breaks some default UI functions on localized servers.
With explode(delimiter, input) I meant a function to split a string into an array based on the occurance of the delimiter string. E.g. explode(",", "123,456") you'd end up with a "123" string and a "456" string.
With substr(input, start, length) I was referring to a substring function that returns part of a string.
EDIT: Drumstix ninja'd me.
