<?php
/******************************************************************************/
/*                                                                            */
/*                       __        ____                                       */
/*                 ___  / /  ___  / __/__  __ _____________ ___               */
/*                / _ \/ _ \/ _ \_\ \/ _ \/ // / __/ __/ -_|_-<               */
/*               / .__/_//_/ .__/___/\___/\_,_/_/  \__/\__/___/               */
/*              /_/       /_/                                                 */
/*                                                                            */
/*                                                                            */
/******************************************************************************/
/*                                                                            */
/* Titre          : Simple CAPTCHA image                                      */
/*                                                                            */
/* URL            : http://www.phpsources.org/scripts339-PHP.htm              */
/* Auteur         : marco12                                                   */
/* Date édition   : 16 Fév 2008                                               */
/*                                                                            */
/******************************************************************************/
 

header("Content-type: image/png"); 
$string = "abcdefghijklmnopqrstuvwxyz0123456789"; 
for($i=0;$i<6;$i++){ 
    $pos = rand(0,36); 
    $str .= $string{$pos}; 
} 

$img_handle = ImageCreate (60, 20) or die ("Impossible de créer l'image");
//Image size (x,y) 
$back_color = ImageColorAllocate($img_handle, 255, 255, 255); 
//Background color RBG 
$txt_color = ImageColorAllocate($img_handle, 0, 0, 0); 
//Texte Couleur RBG
ImageString($img_handle, 31, 5, 0, $str, $txt_color); 
Imagepng($img_handle); 

session_start(); 
$_SESSION['img_number'] = $str; 
?>  

form.php
<form action="result.php" method="post"> 
    <img alt="Nombre aléatoire" src="image.php">
    <input type="text" name="num"><br> 
    <input type="submit" name="submit" value="Check"> 
</form>  

result.php
<?php 

session_start(); 
if($_SESSION['img_number'] != $_POST['num']){ 
    echo'Le nombre ne correspond pas.<br />';
}else{ 
    echo'Le nombre correspond <br />';
}

?>