Write text vertically inside a cell

I am trying to write text vertically inside a cell and I found this code it does work but I don't know how to use it inside the Cell() function because it keeps saying it's undefined it's my first time using FPDF and I'm still trying to learn it so can you please tell me how to make it work

    function TextWithDirection($x, $y, $txt, $direction='R')
    {
        if ($direction=='R')
            $s=sprintf('BT %.2F %.2F %.2F %.2F %.2F %.2F Tm (%s) Tj ET',1,0,0,1,$x*$this->k,($this->h-$y)*$this->k,$this->_escape($txt));
        elseif ($direction=='L')
            $s=sprintf('BT %.2F %.2F %.2F %.2F %.2F %.2F Tm (%s) Tj ET',-1,0,0,-1,$x*$this->k,($this->h-$y)*$this->k,$this->_escape($txt));
        elseif ($direction=='U')
            $s=sprintf('BT %.2F %.2F %.2F %.2F %.2F %.2F Tm (%s) Tj ET',0,1,-1,0,$x*$this->k,($this->h-$y)*$this->k,$this->_escape($txt));
        elseif ($direction=='D')
            $s=sprintf('BT %.2F %.2F %.2F %.2F %.2F %.2F Tm (%s) Tj ET',0,-1,1,0,$x*$this->k,($this->h-$y)*$this->k,$this->_escape($txt));
        else
            $s=sprintf('BT %.2F %.2F Td (%s) Tj ET',$x*$this->k,($this->h-$y)*$this->k,$this->_escape($txt));
        if ($this->ColorFlag)
            $s='q '.$this->TextColor.' '.$s.' Q';
        $this->_out($s);
    } 

R: Left to Right, U: Bottom to Top, D: Top To Bottom, L: Right to Left.