[php] URL format with GET parameters?

Is there a specification somewhere listing the correct way to pass GET variables to a URL?

Normally I do it like this (first variable indicated by ?, second and subsequent indicated by &:

http://www.mysite.com/mypage.html?var1=value1&var2=value2&var3=value3

Are those ? and & specifically needed, and in those order? Could I eliminate the '?' and pass all variables only with the '&' ?

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