PHP Captcha without session

Question

Ok, here is an issue: in the project i\'m working on, we can\'t rely on server-side sessions for any functionality.

The problem is that common captcha solutions fro

Answer 1

Form with validation:

$errorsucc = '';

if (isset($_POST["captcha_check"])) {

    $code = str_decrypt($_POST["captcha_check"]);   

    if (empty($_POST['captcha_code'])) { 
        $errorsucc = '
Please Enter the security code.
';

    } elseif(!( $code == $_POST['captcha_code'] && !empty($code) )) {
        $errorsucc = '
Incorrect Code Entered.
';

    } else {
        $errorsucc = '
Nice, you entered the correct code.
';  
    }
}

$captcha = new CaptchaCode();
$code = str_encrypt($captcha->generateCode(6));
?>


    
    

        
        

            

                
Security Code:
                    

                
                
Enter Code:
                    

                

                

                    
                    

                           
                    
                
            
            
        
    

Generate images just like any other captcha:

/* 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, 0, 26, 26);
    $noise_color = imagecolorallocate($image, 25, 89, 89);
    /* 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);

Download the demo files from this link: Create a Sessionless Captcha in PHP