Numeric Captcha Library

[eluser]Kevin Phillips[/eluser]
I've built a numeric captcha, similar to the one on Drupal (and probably most other cms's)

I've got it working on my sites but would be interested in anyone else views

Code:

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

/*
* A Math Captcha Library that displays a number captcha similar to the drupal captcha.
*
* INSTRUCTIONS
*
* Place this class into you application/library directory and name it kaptcha.php
*
* create MY_Form_validation.php, add this code and save it in the application/libraries folder.
*
* <?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
* class MY_Form_validation extends CI_Form_validation {
*
*   public function kaptcha($value) {
*       $answer = $this->CI->input->post('kaptcha_answer');
*       if($this->CI->kaptcha->validate_kaptcha($value, $answer)) {
*           return TRUE;
*       }
*       return FALSE;
*   }
* }
*
*
* Add this to your controller form validation rules
* $this->form_validation->set_rules('kaptcha', 'Math Question', 'required|is_numeric|kaptcha');
*
* You can either add this to your form using a single line <?php $this->kaptcha->display_kaptcha(); ?>
* or call it as an array <?php $kaptcha = $this->kaptcha->create_kaptcha() ;?> which  will give you three items
* First Number, Second Number and an encrypted answer which needs to be put in a hidden  input value with the
* name and id set to kaptcha_answer.
*
* The CSS is you bit!
*
*
* !IMPORTANT
* Either load this library using the autoload.php or call it from your controller $this->load->library('kaptcha');
* You will need to set an encryption key in your application/config/config.php line 220 $config['encryption_key'] = "";.
* Keys can be generated here http://randomkeygen.com/.
*
*/
class Kaptcha {

    var $CI;
    
    function __construct() {
        $this->CI =& get_instance();
        $this->CI->load->library('encrypt');
        
    }
    
    /*
     * This function allows you to call the kaptcha as a block
     * and insert it in a form as one line of code.
     * <?php $kaptcha = $this->kaptcha->display_kaptcha(); ?>
     */
    public function display_kaptcha() {
        $kaptcha = $this->create_kaptcha();
        
        $display = '';
        $display .= '<span id="kaptcha_inst">This question is for testing whether you are a human visitor and to prevent automated spam submissions.</span>';
        $display .= '<label for="kaptcha"><span>*</span> Math question: <span id="kaptcha_question">'. $kaptcha['first'] .' + '. $kaptcha['second']. ' = </span></label>';
        $display .= '&lt;input type="text" name="kaptcha" id="kaptcha" maxlength="5" /&gt;';
        $display .= '<span id="kaptcha_hint">'.$kaptcha['hint'].'</span>';
        $display .= '&lt;input type="hidden" name="kaptcha_answer" id="kaptcha_answer" value="'. $kaptcha['answer'].'" /&gt; ';
        return $display;
    }
    
    */
    * Function that returns two parts of the math question and an encrypted answer
    */
    public function create_kaptcha() {
        $display = array();
        $display['first'] = rand(1,10);
        $display['second'] = rand(1,10);
        $answer = $display['first'] + $display['second'];
        $display['answer'] = $this->CI->encrypt->encode($answer);
        $display['hint'] = 'Solve this simple math problem and enter the result. E.g. for 1+3, enter 4.';
        return $display;
    }

    */
    * Function that validates the user answer against the encrypted answer
    */
    
    public function validate_kaptcha($kaptcha = null, $answer = null) {
        if($kaptcha && $answer) {
            $value = $this->CI->encrypt->decode($answer);
            if($kaptcha == $value) {
                return TRUE;
            }
        }
        return FALSE;
    }

}

[eluser]Unknown[/eluser]
can you guide me by make a simple implementation?

[eluser]InsiteFX[/eluser]
And how do you validate it before submiting the form?

In mine I check it wirh jQuery before submiting it...