formulaire php htlm / captcha

<?php
if(isset($_GET['message']) && $_GET['message']==1){ 
$message="Erreur saisir un code correct"; 
//echo $message; /*echo ici ou ailleurs dans la page*/ 
}else{ 
$message=NULL; 
} 
?>
<form method="post" action="verif.php">
<input type="text" size="20" maxlength="50" id="nom" name="nom" value="<?php if(isset($_POST['nom'])){echo $_POST['nom'];}else{echo "";}?>" /> 
<br /><input type="text" size="20" maxlength="50" id="prenom" name="prenon" value="<?php if(isset($_POST['prenom'])){echo $_POST['prenom'];}else{echo "";}?>" /> 
<br /><img src="imagecaptcha.php">
<?php echo $message;?>
<br /><input type="text" size="20" maxlength="50" id="code" name="code" value="" /> 
<br /><input type="submit" name="sub" value="envoi" /> 
</form>

<?php
session_start();
if(isset($_POST['code']) && isset($_SESSION['code']) && $_POST['code']===$_SESSION['code']){
echo '<pre>';
print_r($_POST); /*du form.php*/
echo '</pre>';
echo 'ça marche';
/*un traitement*/
/*
mail();
mysql_connect() ...
*/
}else{
header('Location: form.php?message=1');exit;
}
?>

<?php
session_start();
 
/*
* File: CaptchaSecurityImages.php
* Author: Simon Jarvis
* Copyright: 2006 Simon Jarvis
* Date: 03/08/06
* Updated: 07/02/07
* Requirements: PHP 4/5 with GD and FreeType libraries
* Link: http://www.white-hat-web-design.co.uk/articles/php-captcha.php
* 
* This program is free software; you can redistribute it and/or 
* modify it under the terms of the GNU General Public License 
* as published by the Free Software Foundation; either version 2 
* of the License, or (at your option) any later version.
* 
* This program is distributed in the hope that it will be useful, 
* but WITHOUT ANY WARRANTY; without even the implied warranty of 
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 
* GNU General Public License for more details: 
* http://www.gnu.org/licenses/gpl.html
*
*/
 
class CaptchaSecurityImages {
 
   var $font = 'arial.ttf';
 
   function generateCode($characters) {
      /* list all possible characters, similar looking characters and vowels have been removed */
      $possible = '23456789bcdfghjkmnpqrstvwxyz';
      $code = '';
      $i = 0;
      while ($i < $characters) { 
         $code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);
         $i++;
      }
      return $code;
   }
 
   function CaptchaSecurityImages($width='120',$height='40',$characters='6') {
      $code = $this->generateCode($characters);
      /* font size will be 75% of the image height */
      $font_size = $height * 0.75;
      $image = imagecreate($width, $height) or die('Cannot initialize new GD image stream');
      /* set the colours */
      $background_color = imagecolorallocate($image, 255, 255, 255);
      $text_color = imagecolorallocate($image, 20, 40, 100);
      $noise_color = imagecolorallocate($image, 100, 120, 180);
      /* generate random dots in background */
      for( $i=0; $i<($width*$height)/3; $i++ ) {
         imagefilledellipse($image, mt_rand(0,$width), mt_rand(0,$height), 1, 1, $noise_color);
      }
      /* generate random lines in background */
      for( $i=0; $i<($width*$height)/150; $i++ ) {
         imageline($image, mt_rand(0,$width), mt_rand(0,$height), mt_rand(0,$width), mt_rand(0,$height), $noise_color);
      }
      /* create textbox and add text */
      $textbox = imagettfbbox($font_size, 0, $this->font, $code) or die('Error in imagettfbbox function');
      $x = ($width - $textbox[4])/2;
      $y = ($height - $textbox[5])/2;
      imagettftext($image, $font_size, 0, $x, $y, $text_color, $this->font , $code) or die('Error in imagettftext function');
      /* output captcha image to browser */
      header('Content-Type: image/jpeg');
      imagejpeg($image);
      imagedestroy($image);
      $_SESSION['code'] = $code;
   }
 
}
 
$width = isset($_GET['width']) && $_GET['width'] < 600 ? $_GET['width'] : '120';
$height = isset($_GET['height']) && $_GET['height'] < 200 ? $_GET['height'] : '40';
$characters = isset($_GET['characters']) && $_GET['characters'] > 2 ? $_GET['characters'] : '6';
 
$captcha = new CaptchaSecurityImages($width,$height,$characters);
 
?>

<input type="checkbox" name="tpc[experience]" id="experience" onClick="document.getElementById('domaine').style.display = this.checked?null:'none'" style='float:left; margin-top:3px; margin-left:-10px; width:30px;' value="ok" />
<input type="text" name="tpc[domaine]" id="domaine" style="display:none;" />