Class: HN CAPTCHA

This class generates a picture to use in forms that perform CAPTCHA test (Completely Automated Public Turing to tell Computers from Humans Apart). After the test form is submitted a key entered by the user in a text field is compared by the class to determine whether it matches the text in the picture.

The class is a fork of the original released also in this site by Julien Pachet with the name ocr_captcha.

The following enhancements were added:

- Support to make it work with GD library before version 2
- Hacking prevention
- Optional use of Web safe colors
- Limit the number of users attempts
- Display an optional refresh link to generate a new picture with a different key without counting to the user attempts limit verification
- Support the use of multiple random TrueType fonts
- Control the output image by only three parameters: number of text characters and minimum and maximum size preserving the size proportion
- Preserve all request parameters passed to the page via the GET method, so the CAPTCHA test can be added to existing scripts with minimal changes
- Added a debug option for testing the current configuration

All the configuration settings are passed to the class in an array when the object instance is initialized.

The class only needs two function calls to be used: display_form() and validate_submit().

Optional-Class-Extensions:
hn_captcha_X1: add a garbage collector (for 'lost' images) to main class.

Since 24 December 2007, there are different classfiles for PHP 4 and PHP 5, ( merry x-mass <<<-| )

Harto me tenían ya con tanto spam, me pasaba al día más o menos unos 5-10 minutos eliminando comentarios de spam...

Now, you don’t have to register in order to be able to post comments. I managed to install Boriel’s plug-in, based on HN Captcha PHP class...

GeoAddress ist ein WordPress-Plugin zum Erstellen einer Kontakt-/Adressliste die in einer Google-Map mittels Markern dargestellt werden kann...

Firma Konrad Priemer had developed a Wordpress Plugin named GeoAddress w/ the integration of EasyGoogleMap and HN Captcha...

Right now, you have to fill out two forms in order to contact us which is quite annoying. If anybody knows how to integrate the hn_captcha class with forms, please let me know...

Akismet is cool, it really works great, but to really reduce comment spam you need Captcha !...

Various types of spam plugins exist...

Nucleus is a Content Management System (CMS): a powerful set of PHP scripts that allow you to maintain one or more weblogs or online journals.

elists.resynthesize.com provides browsable, searchable archives of electronic music

an online demo-script

Put the files with subdir into the hn_captcha-folder, then the examples should work directly!

Tom 7 has created very nice TrueType-Fonts. They are not under (L)GPL, but also free. Please read his License. Thank you Tom!

... is a very good german Freeware List. Currently are 3 packages available each containing about 14 Fonts and there is also a Linklist to other Font-Sites.

switch to main class PHP 4 / 5

Main Class for PHP 4

Main Class for PHP 5

switch to extension class PHP 4 / 5

class extension that add a garbage collector to main class

class extension that add a garbage collector to main class

Example for the main class

an example how to use the captcha test with existing Forms.

another example of usage with existing forms

Example for the garbage collector extension