If you really don’t need the first element anymore after the loop then you can use the witigo’s second method and if you may need this later in the script then you can use the witigo’s first method.
FYI, the unset() function returns nothing since it is a language construct. It just unset the given variable instead (see PHP Manual) whereas the foreach needs the array as the first argument. So always see php manual once you use a function if you are not sure what the function does for you.