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

class PDF_Ref extends FPDF
{
public $RefActive=false;    //Flag indicating that the index is being processed
public $ChangePage=false;   //Flag indicating that a page break has occurred
public $Reference=array();  //Array containing the references
public $col=0;              //Current column number
public $NbCol;              //Total number of columns
public $y0;                 //Top ordinate of columns

function Header()
{
    if($this->RefActive)
    {
        //Title of index pages
        $this->SetFont('Arial', '', 15);
        $this->Cell(0, 5, 'Index', 0, 1, 'C');
        $this->Ln();
    }
}

function Reference($txt)
{
    $Present=0;
    $size=sizeof($this->Reference);

    //Search the reference in the array
    for ($i=0;$i<$size;$i++){
        if ($this->Reference[$i]['t']==$txt){
            $Present=1;
            $this->Reference[$i]['p'].=', '.$this->PageNo();
        }
    }

    //If not found, add it
    if ($Present==0)
        $this->Reference[]=array('t'=>$txt, 'p'=>$this->PageNo());
}

function CreateReference($NbCol)
{
    //Initialization
    $this->RefActive=true;
    $this->SetFontSize(8);

    //New page
    $this->AddPage();

    //Save the ordinate
    $this->y0=$this->GetY();
    $this->NbCol=$NbCol;
    $size=sizeof($this->Reference);
    $PageWidth=$this->w-$this->lMargin-$this->rMargin;

    for ($i=0;$i<$size;$i++){

        //Handles page break and new position
        if ($this->ChangePage) {
            $this->ChangePage=false;
            $this->y0=$this->GetY()-$this->FontSize-1;
        }

        //LibellLabel
        $str=$this->Reference[$i]['t'];
        $strsize=$this->GetStringWidth($str);
        $this->Cell($strsize+2, $this->FontSize+2, $str, 0, 0, 'R');

        //Dots
        //Computes the widths
        $ColWidth=($PageWidth/$NbCol)-2;
        $w=$ColWidth-$this->GetStringWidth($this->Reference[$i]['p'])-($strsize+4);
        if ($w<15)
            $w=15;
        $nb=$w/$this->GetStringWidth('.');
        $dots=str_repeat('.', (int)$nb-2);
        $this->Cell($w-2, $this->FontSize+2, $dots, 0, 0, 'L');

        //Page number
        $Largeur=$ColWidth-$strsize-$w;
        $this->Cell($Largeur, $this->FontSize+2, $this->Reference[$i]['p'], 0, 1, 'R');
    }
    $this->RefActive=false;
}

function SetCol($col)
{
    //Set position on a column
    $this->col=$col;
    $x=$this->rMargin+$col*($this->w-$this->rMargin-$this->rMargin)/$this->NbCol;
    $this->SetLeftMargin($x);
    $this->SetX($x);
}

function AcceptPageBreak()
{
    if ($this->RefActive) {
        if($this->col<$this->NbCol-1)
        {
            //Go to the next column
            $this->SetCol($this->col+1);
            $this->SetY($this->y0);
            //Stay on the page
            return false;
        }
        else
        {
            //Go back to the first column
            $this->SetCol(0);
            $this->ChangePage=true;
            //Page break
            return true;
        }
    }
    else
    {
        return true;
    }
}
}
?>

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

//Sort function for references
//To be defined by the user to achieve desired results
//This function is case insensitive
function cmp($a, $b) {
    return strnatcmp(strtolower($a['t']), strtolower($b['t']));
}

$pdf=new PDF_Ref();
$pdf->SetFont('Arial', '', 15);

//Page 1
$pdf->AddPage();
$pdf->Cell(0, 5, 'Page 1', 0, 1, 'C');
$pdf->Reference('A');
$pdf->Reference('B');
$pdf->Reference('R');

//Page 2
$pdf->AddPage();
$pdf->Cell(0, 5, 'Page 2', 0, 1, 'C');
$pdf->Reference('R');
$pdf->Reference('a');
$pdf->Reference('A');
$pdf->Reference('g');
$pdf->Reference('G');
$pdf->Reference('N');
for ($i=1;$i<=200;$i++)
    $pdf->Reference('Ref'.$i);

//Alphabetic sort of the references
usort($pdf->Reference, 'cmp');

//Creation of index
$pdf->CreateReference(4);
$pdf->Output();
?>