src/Maths/Geometry/Quadrilateral.php
public function isParallelogram()
    {
        $centerdiag1 = $this->getFirstDiagonal();
        $centerdiag2 = $this->getSecondDiagonal();
        return (bool) Maths::areSamePoint($centerdiag1->getCenter(), $centerdiag2->getCenter());
    }
public function isParallelogram()
    {
        $centerdiag1 = $this->getFirstDiagonal();
        $centerdiag2 = $this->getSecondDiagonal();
        return (bool) Maths::areSamePoint($centerdiag1->getCenter(), $centerdiag2->getCenter());
    }
Test if the quadrilateral is a parallelogram

@return  bool