Circular text

<?php
require('transform.php');

class PDF_CircularText extends PDF_Transform{

    function CircularText($x, $y, $r, $text, $align='top', $kerning=120, $fontwidth=100)
    {
        $kerning/=100;
        $fontwidth/=100;        
        if($kerning==0) $this->Error('Please use values unequal to zero for kerning');
        if($fontwidth==0) $this->Error('Please use values unequal to zero for font width');        
        //get width of every letter
        $t=0;
        for($i=0; $i<strlen($text); $i++){
            $w[$i]=$this->GetStringWidth($text[$i]);
            $w[$i]*=$kerning*$fontwidth;
            //total width of string
            $t+=$w[$i];
        }
        //circumference
        $u=($r*2)*M_PI;
        //total width of string in degrees
        $d=($t/$u)*360;
        $this->StartTransform();
        // rotate matrix for the first letter to center the text
        // (half of total degrees)
        if($align=='top'){
            $this->Rotate($d/2, $x, $y);
        }
        else{
            $this->Rotate(-$d/2, $x, $y);
        }
        //run through the string
        for($i=0; $i<strlen($text); $i++){
            if($align=='top'){
                //rotate matrix half of the width of current letter + half of the width of preceding letter
                if($i==0){
                    $this->Rotate(-(($w[$i]/2)/$u)*360, $x, $y);
                }
                else{
                    $this->Rotate(-(($w[$i]/2+$w[$i-1]/2)/$u)*360, $x, $y);
                }
                if($fontwidth!=1){
                    $this->StartTransform();
                    $this->ScaleX($fontwidth*100, $x, $y);
                }
                $this->SetXY($x-$w[$i]/2, $y-$r);
            }
            else{
                //rotate matrix half of the width of current letter + half of the width of preceding letter
                if($i==0){
                    $this->Rotate((($w[$i]/2)/$u)*360, $x, $y);
                }
                else{
                    $this->Rotate((($w[$i]/2+$w[$i-1]/2)/$u)*360, $x, $y);
                }
                if($fontwidth!=1){
                    $this->StartTransform();
                    $this->ScaleX($fontwidth*100, $x, $y);
                }
                $this->SetXY($x-$w[$i]/2, $y+$r-($this->FontSize));
            }
            $this->Cell($w[$i],$this->FontSize,$text[$i],0,0,'C');
            if($fontwidth!=1){
                 $this->StopTransform();
            }
        }
        $this->StopTransform();
    }

}
?>

<?php
require('circulartext.php');

$pdf = new PDF_CircularText();
$pdf->AddPage();
$pdf->SetFont('Arial','',32);

$text='Circular Text';
$pdf->CircularText(105, 50, 30, $text, 'top');
$pdf->CircularText(105, 50, 30, $text, 'bottom');

$pdf->Output();
?>