I should have included that this can be set globally with $URI::DEFAULT_QUERY_FORM_DELIMITER = ";";.

I know it's mildly controversial with the current RFCs but the & as standard was always a mistake since it effectively made real world separators the incredibly clunky &. As long as you support or know the receiving end supports the semicolon, I think it's the best practice. While I'm telling you kids to get off my lawn, the ?arg[0]=foo&arg[1]=bar crap we got from PHP and ruby webdevs being unable to parse naked lists in order is also a travesty.