Erreur lors de la génération de pdf avec la classe fpdf

 <?php
require('mysql_table.php');
class PDF extends PDF_MySQL_Table
{
protected $ProcessingTable=false;
protected $aCols=array();
protected $TableX;
protected $HeaderColor;
protected $RowColors;
protected $ColorIndex;
function Header()
{
    // Print the table header if necessary
    //if($this->ProcessingTable)
     //   $this->TableHeader();
    // Title
    $this->SetFont('Arial','',14);
    // Logo
$this->Image('logo.png',160,15,30);
// Saut de ligne
$this->Ln(10);
$this->y0 = $this->GetY();
    // Ensure table header is printed
    parent::Header();
}
function TableHeader()
{
    $this->SetFont('Arial','B',12);
    $this->SetX($this->TableX);
    $fill=!empty($this->HeaderColor);
    if($fill)
        $this->SetFillColor($this->HeaderColor[0],$this->HeaderColor[1],$this->HeaderColor[2]);
    foreach($this->aCols as $col)
        $this->Cell($col['w'],6,$col['c'],1,0,'C',$fill);
    $this->Ln();
}

function Row($data)
{
    $this->SetX($this->TableX);
    $ci=$this->ColorIndex;
    $fill=!empty($this->RowColors[$ci]);
    if($fill)
        $this->SetFillColor($this->RowColors[$ci][0],$this->RowColors[$ci][1],$this->RowColors[$ci][2]);
    foreach($this->aCols as $col)
        $this->Cell($col['w'],5,$data[$col['f']],1,0,$col['a'],$fill);
    $this->Ln();
    $this->ColorIndex=1-$ci;
}

function CalcWidths($width, $align)
{
    // Compute the widths of the columns
    $TableWidth=0;
    foreach($this->aCols as $i=>$col)
    {
        $w=$col['w'];
        if($w==-1)
            $w=$width/count($this->aCols);
        elseif(substr($w,-1)=='%')
            $w=$w/100*$width;
        $this->aCols[$i]['w']=$w;
        $TableWidth+=$w;
    }
    // Compute the abscissa of the table
    if($align=='C')
        $this->TableX=max(($this->w-$TableWidth)/2,0);
    elseif($align=='R')
        $this->TableX=max($this->w-$this->rMargin-$TableWidth,0);
    else
        $this->TableX=$this->lMargin;
}

function AddCol($field=-1, $width=-1, $caption='', $align='L')
{
    // Add a column to the table
    if($field==-1)
        $field=count($this->aCols);
    $this->aCols[]=array('f'=>$field,'c'=>$caption,'w'=>$width,'a'=>$align);
}

function Table($link, $query, $prop=array())
{
    // Execute query
    $res=mysqli_query($link,$query) or die('Error: '.mysqli_error($link)."<br>Query: $query");
    // Add all columns if none was specified
    if(count($this->aCols)==0)
    {
        $nb=mysqli_num_fields($res);
        for($i=0;$i<$nb;$i++)
            $this->AddCol();
    }
    // Retrieve column names when not specified
    foreach($this->aCols as $i=>$col)
    {
        if($col['c']=='')
        {
            if(is_string($col['f']))
                $this->aCols[$i]['c']=ucfirst($col['f']);
            else
                $this->aCols[$i]['c']=ucfirst(mysqli_fetch_field_direct($res,$col['f'])->name);
        }
    }
    // Handle properties
    if(!isset($prop['width']))
        $prop['width']=0;
    if($prop['width']==0)
        $prop['width']=$this->w-$this->lMargin-$this->rMargin;
    if(!isset($prop['align']))
        $prop['align']='C';
    if(!isset($prop['padding']))
        $prop['padding']=$this->cMargin;
    $cMargin=$this->cMargin;
    $this->cMargin=$prop['padding'];
    if(!isset($prop['HeaderColor']))
        $prop['HeaderColor']=array();
    $this->HeaderColor=$prop['HeaderColor'];
    if(!isset($prop['color1']))
        $prop['color1']=array();
    if(!isset($prop['color2']))
        $prop['color2']=array();
    $this->RowColors=array($prop['color1'],$prop['color2']);
    // Compute column widths
    $this->CalcWidths($prop['width'],$prop['align']);
    // Print header
    $this->TableHeader();
    // Print rows
    $this->SetFont('Arial','',11);
    $this->ColorIndex=0;
    $this->ProcessingTable=true;
    while($row=mysqli_fetch_array($res))
        $this->Row($row);
    $this->ProcessingTable=false;
    $this->cMargin=$cMargin;
    $this->aCols=array();
}
}

// Connect to database
$link = mysqli_connect('localhost','test','test_','test');

$pdf = new PDF();
$pdf->AddPage();
// First table: output all columns
$pdf->Table($link,'SELECT date,details,sender,content,amount,check_status FROM int_transfer WHERE user_id = 142 UNION SELECT date,details,sender,content,amount,check_status FROM tran_acct WHERE user_id = 142 UNION SELECT date,details,sender,content,amount,check_status FROM int_transfer_admin WHERE user_id = 142 ORDER BY date DESC');
$pdf->AddPage();
// Second table: specify 3 columns
$pdf->AddCol('date',25,'','C');
$pdf->AddCol('details',20,'Type');
$pdf->AddCol('sender',30,'Beneficiary','R'); 
$pdf->AddCol('content',60,'Details ','C');
$pdf->AddCol('amount',20,'Amount');
$pdf->AddCol('check_status',30,'Status','C');

$prop = array('HeaderColor'=>array(255,150,100),
            'color1'=>array(210,245,255),
            'color2'=>array(255,255,210),
            'padding'=>2);
$pdf->Table($link,'SELECT date,details,sender,content,amount,check_status FROM int_transfer WHERE user_id = 142 UNION SELECT date,details,sender,content,amount,check_status FROM tran_acct WHERE user_id = 142 UNION SELECT date,details,sender,content,amount,check_status FROM int_transfer_admin WHERE user_id = 142 ORDER BY date DESC',$prop);
$pdf->Output();

?>