public function commonItems()
    {
        return array_intersect(array_keys($this->input->getColumnsInfo()),
            array_keys($this->output->getColumnsInfo()));
    }
public function commonItems()
    {
        return array_intersect(array_keys($this->input->getColumnsInfo()),
            array_keys($this->output->getColumnsInfo()));
    }
public function commonItems ( ) { return array_intersect ( array_keys ( $ this -> input -> getColumnsInfo ( ) ) , array_keys ( $ this -> output -> getColumnsInfo ( ) ) ) ; }
Return itemes that same on both sides

@return array
Return itemes that same on both sides