Links and flowing text

This tutorial explains how to insert links (internal and external) and shows a new text writing mode. It also contains a rudimentary HTML parser. 
<?php
require('fpdf.php');

class PDF extends FPDF
{
var $B;
var $I;
var $U;
var $HREF;

function PDF($orientation='P',$unit='mm',$format='A4')
{
    //Call parent constructor
    $this->FPDF($orientation,$unit,$format);
    //Initialization
    $this->B=0;
    $this->I=0;
    $this->U=0;
    $this->HREF='';
}

function WriteHTML($html)
{
    //HTML parser
    $html=str_replace("\n",' ',$html);
    $a=preg_split('/<(.*)>/U',$html,-1,PREG_SPLIT_DELIM_CAPTURE);
    foreach($a as $i=>$e)
    {
        if($i%2==0)
        {
            //Text
            if($this->HREF)
                $this->PutLink($this->HREF,$e);
            else
                $this->Write(5,$e);
        }
        else
        {
            //Tag
            if($e{0}=='/')
                $this->CloseTag(strtoupper(substr($e,1)));
            else
            {
                //Extract attributes
                $a2=explode(' ',$e);
                $tag=strtoupper(array_shift($a2));
                $attr=array();
                foreach($a2 as $v)
                    if(ereg('^([^=]*)=["\']?([^"\']*)["\']?$',$v,$a3))
                        $attr[strtoupper($a3[1])]=$a3[2];
                $this->OpenTag($tag,$attr);
            }
        }
    }
}

function OpenTag($tag,$attr)
{
    //Opening tag
    if($tag=='B' or $tag=='I' or $tag=='U')
        $this->SetStyle($tag,true);
    if($tag=='A')
        $this->HREF=$attr['HREF'];
    if($tag=='BR')
        $this->Ln(5);
}

function CloseTag($tag)
{
    //Closing tag
    if($tag=='B' or $tag=='I' or $tag=='U')
        $this->SetStyle($tag,false);
    if($tag=='A')
        $this->HREF='';
}

function SetStyle($tag,$enable)
{
    //Modify style and select corresponding font
    $this->$tag+=($enable ? 1 : -1);
    $style='';
    foreach(array('B','I','U') as $s)
        if($this->$s>0)
            $style.=$s;
    $this->SetFont('',$style);
}

function PutLink($URL,$txt)
{
    //Put a hyperlink
    $this->SetTextColor(0,0,255);
    $this->SetStyle('U',true);
    $this->Write(5,$txt,$URL);
    $this->SetStyle('U',false);
    $this->SetTextColor(0);
}
}

$html='You can now easily print text mixing different
styles : <B>bold</B>, <I>italic</I>, <U>underlined</U>, or
<B><I><U>all at once</U></I></B>!<BR>You can also insert links
on text, such as <A HREF="http://www.fpdf.org">www.fpdf.org</A>,
or on an image: click on the logo.';

$pdf=new PDF();
//First page
$pdf->AddPage();
$pdf->SetFont('Arial','',20);
$pdf->Write(5,'To find out what\'s new in this tutorial, click ');
$pdf->SetFont('','U');
$link=$pdf->AddLink();
$pdf->Write(5,'here',$link);
$pdf->SetFont('');
//Second page
$pdf->AddPage();
$pdf->SetLink($link);
$pdf->Image('logo.png',10,10,30,0,'','http://www.fpdf.org');
$pdf->SetLeftMargin(45);
$pdf->SetFontSize(14);
$pdf->WriteHTML($html);
$pdf->Output();
?>
The new method to print text is Write(). It is very close to MultiCell(); the differences are: So it allows to write a chunk of text, alter the font style, then continue from the exact place we left it. On the other hand, you cannot full justify it.

The method is used on the first page to put a link pointing to the second one. The beginning of the sentence is written in regular style, then we switch to underline and finish it. The link is created with AddLink(), which returns a link identifier. The identifier is passed as third parameter of Write(). Once the second page is created, we use SetLink() to make the link point to the beginning of the current page.

Then we put an image with a link on it. An external link points to an URL (HTTP, mailto...). The URL is simply passed as last parameter of Image(). Note that external links do not work when the PDF is displayed inside Netscape's plug-in.

Finally, the left margin is moved after the image with SetLeftMargin() and some text in HTML format is output. An HTML parser is used for this, based on the regular expression splitting function preg_split() and the option PREG_SPLIT_DELIM_CAPTURE (introduced in PHP 4.0.5) which allows to fetch the separators as well (in this case the tags). If you use an older version of PHP, replace the line with this one: 
$a=preg_split('/[<>]/',$html);
which is less strict but gives the same results with valid HTML.
Recognized tags are <B>, <I>, <U>, <A> and <BR>; the others are ignored. The parser also makes use of the Write() method. An external link is put the same way as an internal one (third parameter of Write()).
Note that Cell() also allows to put links.