PHP中的动态矩阵[关闭]

I have written the PHP code below in order to create a dynamic matrix with different count of columns per row but PHPStorm says the row variable is not defined. please help.

class reply
{
    public $text;
    private $row = array(array());
    private $rowIndex = 0;
    private $colIndex = 0;

    public function Add($menu)
    {
        $this->$row[$this->rowIndex][$this->colIndex] = $menu;
        $this->colIndex++;
    }

    public function NextRow()
    {
        $this->rowIndex++;
        $this->colIndex = 0;
    }
}

$this->$row is incorrect, it should be $this->row.