public function unshift(Period $interval, Period ...$intervals): void
    {
        $this->intervals = array_merge([$interval], $intervals, $this->intervals);
    }
public function unshift(Period $interval, Period ...$intervals): void
    {
        $this->intervals = array_merge([$interval], $intervals, $this->intervals);
    }
public function unshift ( Period $ interval , Period ... $ intervals ) : void { $ this -> intervals = array_merge ( [ $ interval ] , $ intervals , $ this -> intervals ) ; }
Adds new intervals at the front of the sequence.

The sequence is re-indexed after addition

@param Period ...$intervals
Adds new intervals at the front of the sequence .