i25 barcodes

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

// based on the Code 39 script from The-eh
class PDF_i25 extends FPDF
{
function i25($xpos, $ypos, $code, $basewidth=1, $height=10){

    $wide = $basewidth;
    $narrow = $basewidth / 3 ;

    // wide/narrow codes for the digits
    $barChar['0'] = 'nnwwn';
    $barChar['1'] = 'wnnnw';
    $barChar['2'] = 'nwnnw';
    $barChar['3'] = 'wwnnn';
    $barChar['4'] = 'nnwnw';
    $barChar['5'] = 'wnwnn';
    $barChar['6'] = 'nwwnn';
    $barChar['7'] = 'nnnww';
    $barChar['8'] = 'wnnwn';
    $barChar['9'] = 'nwnwn';
    $barChar['A'] = 'nn';
    $barChar['Z'] = 'wn';

    // add leading zero if code-length is odd
    if(strlen($code) % 2 != 0){
        $code = '0' . $code;
    }

    $this->SetFont('Arial','',10);
    $this->Text($xpos, $ypos + $height + 4, $code);
    $this->SetFillColor(0);

    // add start and stop codes
    $code = 'AA'.strtolower($code).'ZA';

    for($i=0; $i<strlen($code); $i=$i+2){
        // choose next pair of digits
        $charBar = $code[$i];
        $charSpace = $code[$i+1];
        // check whether it is a valid digit
        if(!isset($barChar[$charBar])){
            $this->Error('Invalid character in barcode: '.$charBar);
        }
        if(!isset($barChar[$charSpace])){
            $this->Error('Invalid character in barcode: '.$charSpace);
        }
        // create a wide/narrow-sequence (first digit=bars, second digit=spaces)
        $seq = '';
        for($s=0; $s<strlen($barChar[$charBar]); $s++){
            $seq .= $barChar[$charBar][$s] . $barChar[$charSpace][$s];
        }
        for($bar=0; $bar<strlen($seq); $bar++){
            // set lineWidth depending on value
            if($seq[$bar] == 'n'){
                $lineWidth = $narrow;
            }else{
                $lineWidth = $wide;
            }
            // draw every second value, because the second digit of the pair is represented by the spaces
            if($bar % 2 == 0){
                $this->Rect($xpos, $ypos, $lineWidth, $height, 'F');
            }
            $xpos += $lineWidth;
        }
    }
}
}

?>

<?php
require('i25.php');

$pdf = new PDF_i25();
$pdf->AddPage();
$pdf->i25(90,40,'12345678');
$pdf->Output();
?>