added functionality to period

ComplexPeriod.php

<?php

class ComplexPeriod extends DatePeriod
{
    public function __construct($start, $end)
    {
        parent::__construct(
            new \DateTime(date("Y-m-d", strtotime($start))),
			new \DateInterval('P1D'),
			new \DateTime(date("Y-m-d", strtotime($end)))
		);
    }
    
    public function toArray($format = 'Y-m-d')
    {
        $result = [];
        foreach($this as $date) {
            $result[] = $date->format($format);
        }
        
        return $result;
    }
    
    public function diff()
    {
        return $this->getStartDate()->diff($this->getEndDate());
    }
    
    public function overlaps(\DatePeriod $period)
    {
        $start1 = $this->getStartDate()->format('Ymd');
        $end1 = $this->getEndDate()->format('Ymd');
        
        $start2 = $period->getStartDate()->format('Ymd');
        $end2 = $period->getEndDate()->format('Ymd');
        
        return $start1 < $start2 || $end1 > $end2;
    }
}