اول باید یه فایل php بسازید که حاوی کلاسی برای تولید عکس امنیتی است.
<?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',$height='40',$c haracters='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['security_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);
?>
بعد از ذخیره این فایل مثلا تحت نام securityImage.php کافیست داخل فرم خودتون سورس تگ img را به این فایل لینک کنید بطوریکه :
<img src="securityImage.php" />
تا اینجا کد امنیتی تولید و در فرم نمایش داده شده حال کافیست تکست باکسی قرار دهید تا در هنگام تایید شدن فرم (submit) مقدار آن با رشته نمایش داده شده در عکس مقایسه گردد :
فرض کنید تکست باکس به فرمت زیر باشد:
<input id="security_code" name="security_code" type="text" />
کد تایید صحت تصویر امنیتی :
<?php
session_start();
if(($_SESSION['security_code'] == $_POST['security_code']) && (!empty($_SESSION['security_code'])) ) {
// Insert you code for processing the form here, e.g emailing the submission, entering it into a database.
unset($_SESSION['security_code']);
} else {
// Insert your code for showing an error message here
}
?>