Fit Text to MultiCell in PDF Document Using PHP FPDF Library.

This method is an extension of Cell() allowing to output text with either character spacing or horizontal scaling. The first 8 parameters are the same as Cell(). The additional parameters are:

CellFit(float w [, float h [, string txt [, mixed border [, int ln [, string align [, boolean fill [, mixed link [, boolean scale [, boolean force]]]]]]]]])

## scale
false: character spacing
true: horizontal scaling

## force

false: only space/scale if necessary (not when text is short enough to fit)
true: always space/scale

## The following four methods are also provided for convenience, allowing all combinations of scale/force, and using only the 8 parameters of Cell():

CellFitScale()
CellFitScaleForce()
CellFitSpace()
CellFitSpaceForce()

cellfit.php

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

class FPDF_CellFit extends FPDF
{
    //Cell with horizontal scaling if text is too wide
    function CellFit($w, $h=0, $txt='', $border=0, $ln=0, $align='', $fill=false, $link='', $scale=false, $force=true)
    {
        //Get string width
        $str_width=$this->GetStringWidth($txt);

        //Calculate ratio to fit cell
        if($w==0)
            $w = $this->w-$this->rMargin-$this->x;
        $ratio = ($w-$this->cMargin*2)/$str_width;

        $fit = ($ratio < 1 || ($ratio > 1 && $force));
        if ($fit)
        {
            if ($scale)
            {
                //Calculate horizontal scaling
                $horiz_scale=$ratio*100.0;
                //Set horizontal scaling
                $this->_out(sprintf('BT %.2F Tz ET',$horiz_scale));
            }
            else
            {
                //Calculate character spacing in points
                $char_space=($w-$this->cMargin*2-$str_width)/max(strlen($txt)-1,1)*$this->k;
                //Set character spacing
                $this->_out(sprintf('BT %.2F Tc ET',$char_space));
            }
            //Override user alignment (since text will fill up cell)
            $align='';
        }

        //Pass on to Cell method
        $this->Cell($w,$h,$txt,$border,$ln,$align,$fill,$link);

        //Reset character spacing/horizontal scaling
        if ($fit)
            $this->_out('BT '.($scale ? '100 Tz' : '0 Tc').' ET');
    }

    //Cell with horizontal scaling only if necessary
    function CellFitScale($w, $h=0, $txt='', $border=0, $ln=0, $align='', $fill=false, $link='')
    {
        $this->CellFit($w,$h,$txt,$border,$ln,$align,$fill,$link,true,false);
    }

    //Cell with horizontal scaling always
    function CellFitScaleForce($w, $h=0, $txt='', $border=0, $ln=0, $align='', $fill=false, $link='')
    {
        $this->CellFit($w,$h,$txt,$border,$ln,$align,$fill,$link,true,true);
    }

    //Cell with character spacing only if necessary
    function CellFitSpace($w, $h=0, $txt='', $border=0, $ln=0, $align='', $fill=false, $link='')
    {
        $this->CellFit($w,$h,$txt,$border,$ln,$align,$fill,$link,false,false);
    }

    //Cell with character spacing always
    function CellFitSpaceForce($w, $h=0, $txt='', $border=0, $ln=0, $align='', $fill=false, $link='')
    {
        //Same as calling CellFit directly
        $this->CellFit($w,$h,$txt,$border,$ln,$align,$fill,$link,false,true);
    }
}
?>

index.php

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

$txt_short = 'This text is short enough.';
$txt_long = 'This text is way too long.';
for ($i = 1; $i <= 2; $i++)
    $txt_long.=' '.$txt_long;

$pdf = new FPDF_CellFit();
$pdf->AddPage();
$pdf->SetFillColor(0xff,0xff,0x99);

$pdf->SetFont('Arial','B',16);
$pdf->Write(10,'Cell');
$pdf->SetFont('');
$pdf->Ln();
$pdf->Cell(0,10,$txt_short,1,1);
$pdf->Cell(0,10,$txt_long,1,1);
$pdf->Ln(20);

$pdf->SetFont('','B');
$pdf->Write(10,'CellFitScale');
$pdf->SetFont('');
$pdf->Write(10,' (horizontal scaling only if necessary)');
$pdf->Ln();
$pdf->CellFitScale(0,10,$txt_short,1,1);
$pdf->CellFitScale(0,10,$txt_long,1,1,'',1);
$pdf->Ln();

$pdf->SetFont('','B');
$pdf->Write(10,'CellFitScaleForce');
$pdf->SetFont('');
$pdf->Write(10,' (horizontal scaling always)');
$pdf->Ln();
$pdf->CellFitScaleForce(0,10,$txt_short,1,1,'',1);
$pdf->CellFitScaleForce(0,10,$txt_long,1,1,'',1);
$pdf->Ln(20);

$pdf->SetFont('','B');
$pdf->Write(10,'CellFitSpace');
$pdf->SetFont('');
$pdf->Write(10,' (character spacing only if necessary)');
$pdf->Ln();
$pdf->CellFitSpace(0,10,$txt_short,1,1);
$pdf->CellFitSpace(0,10,$txt_long,1,1,'',1);
$pdf->Ln();

$pdf->SetFont('','B');
$pdf->Write(10,'CellFitSpaceForce');
$pdf->SetFont('');
$pdf->Write(10,' (character spacing always)');
$pdf->Ln();
$pdf->CellFitSpaceForce(0,10,$txt_short,1,1,'',1);
$pdf->CellFitSpaceForce(0,10,$txt_long,1,1,'',1);

$pdf->Output();
?>