# Captcha: <?phpsession_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++; } $_SESSION['security_code'] = $code; 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($image); }}$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);?># Form.php :<?phpsession_start();?> <img src="CaptchaSecurityImages.php?width=100&height=40&characters=5" /><br /> <label for="security_code">Security Code: </label><input id="security_code" name="security_code" type="text" value="<?php echo $_SESSION['security_code']; ?>"/><br /># What it does is outputs a captcha image with a textfield where is a security code what is not same as text in captcha image, the text in value is a code what was value what was one session back, lets say i go webit displays me captcha "HELLO" (image), and outputs field with nothing inside it, now i do refresh:the captcha is now "YOYOA" and the textfield has now value "HELLO", any suggs?