private function setPerPage()
    {
        if ($this->hasInput('per_page'))
        {
            $per_page_input = $this->getInput('per_page');

            if ($this->isValidPageNumber($per_page_input)) {
                $this->perPage = $per_page_input;
            }
            else if ($per_page_input == 'all')
            {
                $this->perPage = 'all';
            }
        }
    }