GM Captcha

A simple captcha (and honeypot) implementation for WordPress.

It requires PHP 5.4+.

Table of Contents

• Add to your projects
• Usage
  • Print Fields
  • Check Value
  • Configure
    • Change Defaults
    • Function Arguments
  • Honeypot
• Notes
• License and Credits

Add to your projects

In composer.json add "zoomlab/captcha": "dev-master" to require object and "https://github.com/Giuseppe-Mazzapica/GMCaptcha" to repositories array.

Something like:

"repositories": [
    {
        "type": "vcs",
        "url": "https://github.com/Giuseppe-Mazzapica/GMCaptcha"
    }
],
"require": {
    "php": ">=5.4",
    "zoomlab/captcha": "dev-master"
}

Usage

Print Fields

By default GM Captcha prints 4 fields:

• the captcha image
• a text field where insert the solution
• an hidden field needed for verification
• an honeypot field

the only thing needed to print this field is just call the function GM\captcha(). Nothing else.

Tha function will not create the form, will not add any style, and fields have a minimal markup to easy the styling.

Check Value

When the form is submitted, the only thing needed to check the captcha is call GM\check_captcha().

The function will autodetected everything and return TRUE if the entered value is the right one.

Configure

GM Captcha is very flexible, and allow to configure pretty everything. There are 2 ways to configure the output:

• change the defaults
• pass arguments to GM\captcha()

Of course, both methods can be used togheter and customization passed to function will always overwrite defaults.

Change Defaults

Defaults can be changed using some filter hooks:

• 'gmcaptcha_base_img' to customize the base image for captcha. Hooked functions must return a full url

• 'gmcaptcha_default_size' to customize the captcha size. Hooked functions must return a 2-items array: 1st is width, 2nd is height

• 'gmcaptcha_defaults' to customize different aspects of the captcha. Hooked functions must return an array, where accepted key/default values are:

     $options = [
       'lines'     => 10, // number of  lines to create "noise"
       'dots'      => 100, // number of dots to create "noise"
       'color'     => '7d1ac5', // foreground color, used for captcha code and noise
       'font'      => "/BrokenGlass.ttf", // the font. Must be an absolute path to a .ttf file
       'chars_num' => 4 // number of characters in the captcha code
     ];

• 'gmcaptcha_container' advanced filter that allow to completely customize the Pimple container used by plugin

Function Arguments

The function GM\captcha() can take an array of arguments to customize the appearance of captcha. This array is identical to the one that should be returned on the 'gmcaptcha_defaults' filter, plus 2 other args: 'width' and 'height'.

An example of fully customized function:

GM\captcha([
  'lines'     => 50,
  'dots'      => 0,
  'color'     => 'FF0000',
  'font'      => "/my/theme/path/fonts/custom.ttf",
  'chars_num' => 6,
  'width'     => 300,
  'height'    => 150
]);

Please note that 'width' and 'height' arguments works only if both are used: if only one is set, it will be ignored.

Honeypot

As said, GM Captcha embed a simple honeypot check: is just a text field hidden via inline style (on parent span) that must be empty, and if some robots will fill that field validation fail.

There is no additional validation to make for the honeypot works, all is handled via GM\check_captcha().

However, is possible disable the honeypot returning an empty value on 'gmcaptcha_use_honeypot' filter hook:

add_filter('gmcaptcha_use_honeypot', '__return_false');

Other Customizations

There are few other hooks available:

• 'gmcaptcha_container_class' to customize the class for the div that wrap the captcha fields (empty by default)
• 'gmcaptcha_label' to customize the text shown next to the text field, default: __('Type the captcha:', 'gmcaptcha')

All the (few) strings used in the plugin are translatable, the text domain is 'gmcaptcha' and plugins already comes with italian translation.

Notes

To create the images the plugin uses an extension of core WP_Image_Editor classes, so auto-choose as image driver the first available from ImageMagik an GD using wp_get_image_editor. Image quality is better when ImageMagik is used (default when available).

To re-generate the image upon click (when unreadable code is shown) plugin uses a little javascript script (971 byte in minimized version). This script require jQuery (properly enqueued using wp_enqueue_script). Minimized version is automatically used when WP_DEBUG is set to FALSE.

License and Credits

GM Captcha is released under GPL2+. It makes use of third party scripts and assets:

• Pimple by Fabien Potencier that is released under MIT

• the font 'Broken Glass' designed by JLH Fonts and released under public domain.