Inserting captcha into form

I have got a free working captcha from www.white-hat-web-design.co.uk. I tried it & it works fine. I modified some variables so I can insert it into my form. Even after I modified it ..It's still working fine. When I inserted it into my form it partly worked. As when the user leaves the captcha field empty, it asks him/her to re-enter the captcha again & stops sending the form..This is fine but if the user enters any characters in the captcha field..it validates them whatever the characters are ... it doesn't matter if they match or not. I included the codes of the working captcha alone, the partly working captcha after being inserted in the form & the codes for generating the image. I want to know where the error is.

Working Captcha

<?php 
session_start();

if( isset($_POST['submit'])) {
   if( $trimmed['Captcha'] == $_POST['Captcha'] && !empty($trimmed['Captcha'] ) ) {
		// Insert you code for processing the form here, e.g emailing the submission, entering it into a database. 
		echo 'Thank you. Your message said "'.$_POST['message'].'"';
		unset($trimmed['Captcha']);
   } else {
		// Insert your code for showing an error message here
		echo 'Sorry, you have provided an invalid security code';
   }
} else {
?>

	<form action="form.php" method="post">
		<label for="name">Name: </label><input type="text" name="name" id="name" /><br />
		<label for="email">Email: </label><input type="text" name="email" id="email" /><br />
		<label for="message">Message: </label><textarea rows="5" cols="30" name="message" id="message"></textarea><br />
		<img src="CaptchaSecurityImages.php?width=100&height=40&characters=5" /><br />
		<label for="Captcha">Security Code: </label><input id="Captcha" name="Captcha" type="text" /><br />
		<input type="submit" name="submit" value="Submit" />
	</form>

<?php
	}
?>

Code (markup):

Partly Working

   // Check for a Captcha:
  if( isset($_POST['submit'])) {
	if ($trimmed['Captcha'] == $_POST['Captcha'] && !empty($trimmed['Captcha'])) {
	$ccap = mysqli_real_escape_string 
	($dbc, $trimmed['Captcha']);
	echo "Working Fine";
 unset($trimmed['Captcha']);
 } else {
 echo "Not Working";
 }
}

Code (markup):

The Image Generation Codes

<?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, 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);
		$trimmed['Captcha'] = $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);

?>

Code (markup):

One more thing I want to know is how to add a button that refreshes the image when clicked without refreshing the whole page in case the image was not clear.

 

too complex man,
use recaptcha.net it has all features u need - that with refresh button too

 

Try phpclasses.org class for CAPTCHA, very easy to implement.

 

recaptcha.net looks very good & seems very professional but I can't use it currently as I didn't buy a domain yet. I'm learning & testing on local host. Another reason is that I don't wanna rely on other service providers as I don't know anybody who used it & I can't know the quality of the service.

 

Thank you...very useful. Many captchas to choose from...