Layers

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

class PDF_Layer extends FPDF
{
protected $layers = array();
protected $current_layer = -1;
protected $open_layer_pane = false;

function AddLayer($name, $isUTF8=false, $visible=true)
{
    if(!$isUTF8)
        $name = $this->_UTF8encode($name);
    $this->layers[] = array('name'=>$name, 'visible'=>$visible);
    return count($this->layers)-1;
}

function BeginLayer($id)
{
    $this->EndLayer();
    $this->_out('/OC /OC'.$id.' BDC');
    $this->current_layer = $id;
}

function EndLayer()
{
    if($this->current_layer>=0)
    {
        $this->_out('EMC');
        $this->current_layer = -1;
    }
}

function OpenLayerPane()
{
    $this->open_layer_pane = true;
}

function _endpage()
{
    $this->EndLayer();
    parent::_endpage();
}

function _enddoc()
{
    if($this->PDFVersion<'1.5')
        $this->PDFVersion='1.5';
    parent::_enddoc();
}

function _putlayers()
{
    foreach($this->layers as $id=>$layer)
    {
        $this->_newobj();
        $this->layers[$id]['n'] = $this->n;
        $this->_put('<</Type /OCG /Name '.$this->_textstring($layer['name']).'>>');
        $this->_put('endobj');
    }
}

function _putresources()
{
    $this->_putlayers();
    parent::_putresources();
}

function _putresourcedict()
{
    parent::_putresourcedict();
    $this->_put('/Properties <<');
    foreach($this->layers as $id=>$layer)
        $this->_put('/OC'.$id.' '.$layer['n'].' 0 R');
    $this->_put('>>');
}

function _putcatalog()
{
    parent::_putcatalog();
    $l = '';
    $l_off = '';
    foreach($this->layers as $layer)
    {
        $l .= $layer['n'].' 0 R ';
        if(!$layer['visible'])
            $l_off .= $layer['n'].' 0 R ';
    }
    $this->_put("/OCProperties <</OCGs [$l] /D <</OFF [$l_off] /Order [$l]>>>>");
    if($this->open_layer_pane)
        $this->_put('/PageMode /UseOC');
}
}
?>

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

$pdf = new PDF_Layer();

// Define layers
$l1 = $pdf->AddLayer('Layer 1');
$l2 = $pdf->AddLayer('Layer 2');

// Open layer pane in PDF viewer
$pdf->OpenLayerPane();

$pdf->AddPage();
$pdf->SetFont('Arial','',15);
$pdf->Write(8,"This line doesn't belong to any layer.\n");

// First layer
$pdf->BeginLayer($l1);
$pdf->Write(8,"This line belongs to Layer 1.\n");
$pdf->EndLayer();

// Second layer
$pdf->BeginLayer($l2);
$pdf->Write(8,"This line belongs to Layer 2.\n");
$pdf->EndLayer();

$pdf->Output();
?>