Titoli colonne in fpdf

[mandrake_01]

Ciao, sto utilizzando fpdf per generare una stampa pdf.
Utilizzo il tutorial n.5 che ho modificato in questo modo:

class PDF extends FPDF
{
//Load data
function LoadData($file)
{
    //Path file da stampare
    $dir = 'class/fpdf/filetoprint/';
    $file= $dir. $file;

    //Read file lines
    $lines=file($file);
    $data=array();
    foreach($lines as $line)
        $data[]=explode(';',chop($line));
    return $data;
}

//Better table
function ImprovedTable($header,$data)
{
    //Column widths
    $w=array(10,11,40,55,30,7,8,7,10,10);
    //Header
    for($i=0;$i<count($header);$i++)
        $this->Cell($w[$i],7,$header[$i],1,0,'L');
    $this->Ln();

    //Data
    foreach($data as $row)
    {
        $this->Cell($w[0],4,$row[0],'1',0,'L',$fill);
        $this->Cell($w[1],4,$row[1],'1',0,'L',$fill);
        $this->Cell($w[2],4,$row[2],'1',0,'L',$fill);
        $this->Cell($w[3],4,$row[3],'1',0,'L',$fill);
        $this->Cell($w[4],4,$row[4],'1',0,'L',$fill);
        $this->Cell($w[5],4,$row[5],'1',0,'C',$fill);
        $this->Cell($w[6],4,$row[6],'1',0,'C',$fill);
        $this->Cell($w[7],4,$row[7],'1',0,'C',$fill);
        $this->Cell($w[8],4,$row[8],'1',0,'C',$fill);
        $this->Cell($w[9],4,$row[9],'1',0,'C',$fill);
        $this->Ln();
    }
    //Closure line
    $this->Cell(array_sum($w),0,'','T');
}

}

$pdf=new PDF();
//Column titles
$header=array('NUM','COD','MARCA','CATEGORIA','COLORE','STG','TIPO','SE','TG','QTA');
//Data loading
$data=$pdf->LoadData('articoli.txt');
$pdf->SetFont('Arial','',6);
$pdf->AddPage();
$pdf->ImprovedTable($header,$data);
$pdf->Output();
?> 

Vorrei poter posizionare ogni elemento dell'header a dx al centro o a sx , come avviene con i dati caricati da loadata.
Ho provato a modificare la funzione

//Header
for($i=0;$i<count($header);$i++)
$this->Cell($w[$i],7,$header[$i],1,0,'L');
$this->Ln();

in questo modo

//Header

foreach($header as $cols)
{
$this->Cell($w[0],6,$cols[0],'1',0,'L',$fill);
$this->Cell($w[1],6,$cols[1],'1',0,'L',$fill);
$this->Cell($w[2],6,$cols[2],'1',0,'L',$fill);
$this->Cell($w[3],6,$cols[3],'1',0,'L',$fill);
$this->Cell($w[4],6,$cols[4],'1',0,'L',$fill);
$this->Cell($w[5],6,$cols[5],'1',0,'C',$fill);
$this->Cell($w[6],6,$cols[6],'1',0,'C',$fill);
$this->Cell($w[7],6,$cols[7],'1',0,'C',$fill);
$this->Cell($w[8],6,$cols[8],'1',0,'C',$fill);
$this->Cell($w[9],6,$cols[9],'1',0,'C',$fill);
$this->Ln();
}
Purtroppo la formattazione viene completamente sballata.. non riesco a capire dove sbaglio.

Mi date una mano?
Grazie
Ciao