CAPTCHA.CLASS.PHP

<?
class CAPTCHA {
	function __construct() {
		//clears the cookies.
		setcookie('captcha_question', '', time() - 3600);
		setcookie('captcha_answers', '', time() - 3600);
		setcookie('captcha_math', '', time() - 3600);
		setcookie('captcha_phrase', '', time() - 3600);
		
		$this->passed_args = func_get_args();
		
		/************************************************************************************************************
		Sets the CAPTCHA depending on the the parameters sent with the connstructor:
		1) Ask the user to answer a question. The arguments are, 
		the question, followed by accepted answers, for example: 
		$captcha = new CAPTCHA("what is your favorite programing language?", "php", "asp", "c++", "actionscript");
		2) Ask the user to solve a math problem, for example: $captcha = new CAPTCHA("2 + 2 * 5");
		3) Ask the user to copy a phrase, for example: $captcha = new CAPTCHA("I did this in PHP");
		**************************************************************************************************************/
		
		if(count($this->passed_args) > 1) {
			$this->question = $this->passed_args[0];
			$this->answers = array_slice($this->passed_args, 1);
			
			setcookie("captcha_question", $this->passed_args[0]);
			setcookie("captcha_answers", serialize(array_slice($this->passed_args, 1)));
		} else {
			if(preg_match('/^\s*(\d+\s*[+*]\s*)+\d+\s*$/', $this->passed_args[0])) {
				$this->passed_args[0] = str_replace(' ', '', $this->passed_args[0]);
				$this->math = $this->passed_args[0];
				
				setcookie("captcha_math", $this->passed_args[0]);
			} else {
				$this->phrase = $this->passed_args[0];
				
				setcookie("captcha_phrase", $this->passed_args[0]);
			} 
		}
		
	$this->use_image = true;
    }
	
	/*******************************************************
	Solves simple math expressions, does not take brackets.
	Handles multiplication and addition.
	********************************************************/
	
	static private function solve($expression) {
		$products = explode('+', $expression);
		
		//Multiplication.
		foreach($products as $key => $product) {
			$product = explode('*', $product);
			$products[$key] = 1;
			$_prod = $product;
			foreach($product as $number) {
				$products[$key] *= $number;
			}
		}
		
		//Addition.
		$sum = 0;
		
		foreach($products as $number) {
			$sum += $number;
		}
		
		return($sum);
	}
	
	public function display() {
		include('captcha.html.php');
	}
	
	/*********************************************************
	Returns true if the submitted CAPTCHA response is correct.
	**********************************************************/
	
	static public function validate() {
		$valid = false;
		
		//Get the submitted CAPTCHA response.
		if(!isset($_POST['captcha_input_text']) && !isset($_GET['captcha_input_text'])) {
			$captcha_input_text = '';
		} else {
			if(isset($_POST['captcha_input_text'])) {
				$captcha_input_text = $_POST['captcha_input_text'];
			} else {
				$captcha_input_text = $_GET['captcha_input_text'];
			}
		}
		
		
		//Did the user have to reply to a question?
		if(isset($_COOKIE['captcha_question']) && isset($_COOKIE['captcha_answers'])) {
			if(get_magic_quotes_gpc()) {
				$captcha_answers = unserialize(stripslashes($_COOKIE['captcha_answers']));
			} else {
				$captcha_answers = unserialize($_COOKIE['captcha_answers']);
			}
			
			foreach($captcha_answers as $captcha_answer) {
				if(trim(strtolower($captcha_input_text)) == trim(strtolower($captcha_answer))) {
					$valid = true;
				}
			}
		}
		
		//Did the user have to type out a phrase?
		if(isset($_COOKIE['captcha_phrase'])) {
			if(trim(strtolower($captcha_input_text)) == trim(strtolower($_COOKIE['captcha_phrase']))) {
				$valid = true;
			}
		}
		
		//Did the user have to solve a simple math problem?
		if(isset($_COOKIE['captcha_math'])) {
			if(trim($captcha_input_text) == self::solve($_COOKIE['captcha_math'])) {
				$valid = true;
			}
		}
		
		return($valid);
	}
	
	/****************************************************************
	Theese are helper functions that provide conent for the captchas.
	*****************************************************************/
	
	static public function randomString() {
		$letters = range('a', 'z');
		$numbers = range('0', '9');
		
		$randomString = "";
		
		for($i = 0; $i < 6; $i++) {
			if(rand(0, 10) < 5) {
				$randomString .= $letters[mt_rand(0, count($letters) - 1)];
			} else {
				$randomString .= $numbers[mt_rand(0, count($numbers) - 1)];
			}
		}
		
		return($randomString);
	}
	
	//A database solution could be implemented in this case.
	//I just don't feel like doing so at the moment.
	static public function randomQuestion() {
		$questions = array(
			array("montreal's hockey team", "habs", "canadians"),
			array("december 25", "holidays", "christmas", "festivus", "x-mas", "xmas"),
			array("can't be said on tv", "fuck", "piss", "shit", "cunt", "tits", "mother fucker", "cock")
		);
		
		return($questions[mt_rand(0, count($questions) - 1)]);
	}
	
	static public function randomSimpleMath() {
		$max_num = 5;
		$operands = array('*', '+');
		
		$math_expression = mt_rand(0, $max_num);
		
		for($i = 0; $i < 2; $i++) {
			$math_expression .= $operands[mt_rand(0, count($operands) - 1)] . mt_rand(0, $max_num);
		}
		
		return($math_expression);
	}
}
?>

CAPTCHA.IMG.PHP

<?
/***********************************************************************************
This file generates an image based on the captcha string that is saved as a cookie.
************************************************************************************/

if(isset($_COOKIE['captcha_question']) && isset($_COOKIE['captcha_answers'])) {
	$captcha_question = $_COOKIE['captcha_question'];
}

if(isset($_COOKIE['captcha_phrase'])) {
	$captcha_question = $_COOKIE['captcha_phrase'];
}

if(isset($_COOKIE['captcha_math'])) {
	$captcha_question = $_COOKIE['captcha_math'];
}

if(isset($captcha_question)) {
	if(get_magic_quotes_gpc()) {
		$captcha_question = stripslashes($captcha_question);
	}
	
	header("Content-type: image/png");
	
	$font_size = 15;
	$font_angle = mt_rand(-3, 3);
	$font_file = "verdana.ttf";
	$padding = 10;
	
	$gd_bounding_box = imagettfbbox($font_size, $font_angle, $font_file, $captcha_question);
	
	//Width of the captcha image.
	$captcha_image_xs = array($gd_bounding_box[2], $gd_bounding_box[0], $gd_bounding_box[4], $gd_bounding_box[6]);
	sort($captcha_image_xs);
	$captcha_image_width = 0;
	for($i = 0; $i < count($captcha_image_xs) - 1; $i++) {
		$captcha_image_width += $captcha_image_xs[$i + 1] - $captcha_image_xs[$i];
	}
	
	//Height of the captcha image.
	$captcha_image_ys = array($gd_bounding_box[1], $gd_bounding_box[7], $gd_bounding_box[3], $gd_bounding_box[5]);
	sort($captcha_image_ys);
	$captcha_image_height = 0;
	for($i = 0; $i < count($captcha_image_ys) - 1; $i++) {
		$captcha_image_height += $captcha_image_ys[$i + 1] - $captcha_image_ys[$i];
	}

	$captcha_image = imagecreatetruecolor($captcha_image_width + $padding *2, $captcha_image_height + $padding * 2);
	$white = imagecolorallocate($captcha_image, 255, 255, 255);
	$black = imagecolorallocate($captcha_image, 0, 0, 0);
	imagecolortransparent($captcha_image, $white);
	imagefilledrectangle($captcha_image, 0, 0, $captcha_image_width + $padding *2 - 1, $captcha_image_height + $padding *2 - 1, $white);

	imagettftext($captcha_image, $font_size, $font_angle, -$captcha_image_xs[0] + $padding, -$captcha_image_ys[0] + $padding, $black, $font_file, $captcha_question);
	
	imagepng($captcha_image);
	imagedestroy($captcha_image);
}
?>

CAPTCHA.HTML.PHP

<div class="captcha">
<?
if(isset($this->question) && isset($this->answers)) { 
	$captcha_input_class = "captcha_text_box";
	$captcha_challenge = "answer this question";
	$captcha_text = $this->question;
	?>
	
<? } ?>

<? if(isset($this->math)) {
	$captcha_input_class = "captcha_number_box"; 
	$captcha_challenge = "solve this math problem";
	$captcha_text = $this->math;
	?>
	
<? } ?>

<? if(isset($this->phrase)) { 
	$captcha_input_class = "captcha_text_box";
	$captcha_challenge = "copy this text";
	$captcha_text = $this->phrase;
	?>
	
<? } ?>
<label for="captcha_input_text"><?= $captcha_challenge ?>:<br />
<? if($this->use_image) { ?>
	<img src="captcha.img.php" />
<? } else { ?>
	<?= $captcha_text ?>
<? } ?>
</label>
<input type="text" class="<?= $captcha_input_class ?>" id="captcha_input_text" name="captcha_input_text" /> 
<input type="button" value="validate" onclick="sendCaptchaReply();" />
<span id="captcha_response"></span>
</div>

CAPTCHA.JS

function getXMLObject()
{
         var xmlHttp = null;
         try
         {
           xmlHttp = new XMLHttpRequest();
         }
         catch(e)
         {
              try
              {
                  xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
              }
              catch(e)
              {
                   try
                   {
                       xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
                   }
                   catch(e)
                   {
                         xmlHttp = null;
                   }
              }
         }

         return(xmlHttp);
}

var ajax = getXMLObject();

function sendCaptchaReply() {
         ajax.onreadystatechange = confirmCaptcha;

         ajax.open("POST", 'captcha.ajax.php', true);

         var captchaReply = 'captcha_input_text=' +  document.getElementById('captcha_input_text').value;

         ajax.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
	     ajax.setRequestHeader("Content-length", captchaReply.length);
	     ajax.setRequestHeader("Connection", "close");
		 
		 ajax.send(captchaReply);
}

function confirmCaptcha() {
         if(ajax.readyState == 4)
         {
            if(ajax.status == 200)
            {
               document.getElementById('captcha_response').innerHTML = document.getElementById('captcha_input_text').value + ajax.responseText;
			   document.getElementById('captcha_input_text').value = '';
            }
         }
}

CAPTCHA.PHP

CAPTCHA.AJAX.PHP

CAPTCHA.CLASS.PHP

CAPTCHA.IMG.PHP

CAPTCHA.HTML.PHP

CAPTCHA.JS