A simple math based CAPTCHA library for CodeIgniter with various configurable options.

• Supports addition, subtraction, multiplication and division
• Multi-language support
• Questions written in plain English (or your chosen language) in various phrases
• Questions can contain numbers as words, numeric or random
• Answers can be enforced to numeric, words or either
• Add your own question phrases for added randomness

Some examples:

What do you get if you add eight to five?

What is the sum of five and three?

Add ten to ten, what do you get?

What is seven plus six?

or

What is 7 plus 6?

This library is designed to work with CodeIgniter's core Session library. I've tested it with the core Form Validation library, but see no reason why you couldn't use it with an alternative.

The folder structure should match the CodeIgniter folder structure.

1. Copy the application/libraries/mathcaptcha_library.php file to application/libraries/

2. Copy the application/language/english/mathcaptcha_lang.php to application/language/english/

3. If you would like to use another language other than English you will need to duplicate the language file and translate the numbers and phrases respectively

4. Initialise the math CAPTCHA library and include it in your controller. Example below:

    public function myform()
    {
            $this->load->library('mathcaptcha');
            $this->mathcaptcha->init();
        
            $data['math_captcha_question'] = $this->mathcaptcha->get_question();
        
            $this->form_validation->set_rules('math_captcha', 'Math CAPTCHA', 'required|callback__check_math_captcha');
        
            if ($this->form_validation->run() == FALSE)
            {
                $this->load->view('myform', $data);
            }
            else
            {
                $this->load->view('myform', $data);
            }
    }
   

5. Add a callback for the math CAPTCHA form validation if you are using CodeIgniter Form Validation library. Example below:

    function _check_math_captcha($str)
    {
        if ($this->mathcaptcha->check_answer($str))
        {
            return TRUE;
        }
        else
        {
            $this->form_validation->set_message('_check_math_captcha', 'Enter a valid math captcha response.');
            return FALSE;
        }
    }
   

6. Print the $mathcaptcha_question on your form somewhere. Example below:

    <?php echo validation_errors(); ?>
   
    <?php echo form_open(); ?>
   
        <?php echo $math_captcha_question;?>
   
        <?php echo form_input('math_captcha');?>
   
        <?php echo form_submit('submit', 'Submit'); ?>
   
    <?php echo form_close();?>
   

And that's it!

There are some configuration options which you can pass to the library in an associative array when you $this->mathcaptcha->init($config):

• language: This should be set to the language that you want to use. It will default to the language set in the Codeigniter config.php.
• operation: The type of math question to use; addition, subtraction, multiplication, division or random. This will default to addition if not specified.
• question_format: The type of number to include in the question; numeric, word, or random. This will default to word if not specified.
• question_max_number_size: The maximum number size to use in the question. The default is 10, which is also the maximum allowed given the limitations of the language file.
• answer_format: The type of answer that is allowed; word means the user must answer in a word, numeric means the user must enter the number or either for, well, either.

In order to make your installation of math CAPTCHA more unique you can try changing/adding more phrases to the language file. If you add more than 5, adjust the MATHCAPTCHA_NUM_ADDITION_PHRASES and MATHCAPTCHA_NUM_MULTIPLICATION_PHRASES constants in the library file appropriately.

Many thanks to Nico Zimmermann and Michał Śniatała for contributing with code and translations :)

GNU General Public License

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 3 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.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.