Captcha Security Image // Not working in firefox?

[chmpdog]

Hello,

 

Recently I was testing a capatcha on my site (on my localhost, wamp) where I noticed it worked in both chrome and IE, but didnt work in firefox. I think it has something to do with the sessions, but not sure. I have reset all my browser settings, but no dice.

 

Any one knows what is happening?

 

PS: here is the code if you need to see it.

<?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 = 'monofont.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, 128, 0, 0);
	$noise_color = imagecolorallocate($image, 125, 125, 125);
	/* 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, $text_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);

	unset($_SESSION['security_code']);
	$_SESSION['security_code'] = $_SESSION['mycode'] =$code;

}

}

$width = isset($_GET['width']) ? $_GET['width'] : '120';
$height = isset($_GET['height']) ? $_GET['height'] : '40';
$characters = isset($_GET['characters']) && $_GET['characters'] > 1 ? $_GET['characters'] : '6';

$captcha = new CaptchaSecurityImages($width,$height,$characters);

?>

 

Thank-you

 

 

[chmpdog]

I researched it a little it appears to be a firefox 3.0 bug, but is there anyway to update my code to work around it?