Simple, image-based, mathematical captcha, with increasing levels of difficulty for PHP, JavaScript, Python

version 2.6.0

see also:

• ModelView a simple, fast, powerful and flexible MVVM framework for JavaScript
• tico a tiny, super-simple MVC framework for PHP
• LoginManager a simple, barebones agnostic login manager for PHP, JavaScript, Python
• SimpleCaptcha a simple, image-based, mathematical captcha with increasing levels of difficulty for PHP, JavaScript, Python
• Dromeo a flexible, and powerful agnostic router for PHP, JavaScript, Python
• PublishSubscribe a simple and flexible publish-subscribe pattern implementation for PHP, JavaScript, Python
• Importer simple class & dependency manager and loader for PHP, JavaScript, Python
• Contemplate a fast and versatile isomorphic template engine for PHP, JavaScript, Python
• HtmlWidget html widgets, made as simple as possible, both client and server, both desktop and mobile, can be used as (template) plugins and/or standalone for PHP, JavaScript, Python (can be used as plugins for Contemplate)
• Paginator simple and flexible pagination controls generator for PHP, JavaScript, Python
• Formal a simple and versatile (Form) Data validation framework based on Rules for PHP, JavaScript, Python
• Dialect a cross-vendor & cross-platform SQL Query Builder, based on GrammarTemplate, for PHP, JavaScript, Python
• DialectORM an Object-Relational-Mapper (ORM) and Object-Document-Mapper (ODM), based on Dialect, for PHP, JavaScript, Python
• Unicache a simple and flexible agnostic caching framework, supporting various platforms, for PHP, JavaScript, Python
• Xpresion a simple and flexible eXpression parser engine (with custom functions and variables support), based on GrammarTemplate, for PHP, JavaScript, Python
• Regex Analyzer/Composer Regular Expression Analyzer and Composer for PHP, JavaScript, Python

Example:

1. Captcha with Position Distortion:
2. Captcha with Scale Distortion:
3. Captcha with Gradient Background:
4. Captcha with custom pattern background:

// setup
$captcha = (new SimpleCaptcha())
    ->option('secret_key', 'SECRET_KEY')
    ->option('secret_salt', 'SECRET_SALT_')
    ->option('difficulty', 1) // 0 (easy) to 3 (difficult)
    ->option('distortion_type', 1) // 1: position distortion, 2: scale distortion
    ->option('num_terms', 2)
    ->option('max_num_terms', 4) // -1 means constant num_terms
    ->option('min_term', 1)
    ->option('max_term', 21)
    ->option('has_multiplication', true)
    ->option('has_division', true)
    ->option('has_equal_sign', true)
    ->option('color', 0x121212)
    ->option('background', 0xffffff)
;

<!-- use it -->
<?php $captcha->reset(); ?>
<form action="/validate" method="post">
<!-- you can store the captcha hash in the $_SESSION or in $_COOKIE as well -->
<input type="hidden" name="hash" value="<?php echo $captcha->getHash(); ?>" />
Compute result <img src="<?php echo $captcha->getCaptcha(); ?>" /> <input type="text" name="answer" value="" />
<button type="submit">Submit</button>
</form>

// use it
$app->on('/validate', function() use ($captcha) {
    // you can store the captcha hash in the $_SESSION or in $_COOKIE as well
    if ($captcha->validate($_POST['answer'], $_POST['hash']))
    {
    // correct captcha
    }
    else
    {
    // wrong captcha
    }
});