<?php
//500x400 image works well.  Odd sizes may not work.
//Just a simple CMMDC function
function CMMDC($a, $b)
   {
   $cmmdc = 10;
   $ca = $a;
   $cb = $b;
   while($a != $b)
         {
         if($a > $b) { $a = $a - $b; } else { $b = $b - $a; }
         $cmmdc = $a;
         }  
   if(($cmmdc <= 1) || ($cmmdc == ca) || ($cmmdc == cb)) return 10;
   
   return $cmmdc;        
   }

//load the JPG image
$im = imagecreatefromjpeg("guitars-new.jpg");

//get the image dimensions
$size = getimagesize("guitars-new.jpg");
$L=$size[0];
$H=$size[1];

//get the size of puzzle piece
$step=CMMDC($L,$H);  

//determine the number of pieces
$Lv=floor((float)$L/(float)$step);
$Ho=floor((float)$H/(float)$step);

//obtain the puzzle by mixing the pieces
$permut = 10*$Lv*$Ho;
for($i = 0; $i < $permut; $i++)
    {
    $fromx=rand(0,$Lv-1);
    $fromy=rand(0,$Ho-1);

    $tox=rand(0,$Lv-1);
    $toy=rand(0,$Ho-1);    

    //create a new image
    $temp = imagecreatetruecolor($step, $step);

    //copy image into $temp
    imagecopy($temp, $im, 0, 0, $step*$fromx, $step*$fromy, $step, $step);

    //move in place the generated piece
    imagecopy($im, $im, $step*$fromx, $step*$fromy, $step*$tox, $step*$toy, $step, $step);

    //restore the empty piece with the $temp
    imagecopy($im, $temp, $step*$tox, $step*$toy, 0, 0, $step, $step);
    }
    
    //display the puzzle 
    header("Content-type: image/jpeg");
    imagejpeg($im);     
?>