# CAPTCHA Adapters

The following adapters are shipped with Zend Framework by default.

## Zend_Captcha_Word

`Zend_Captcha_Word` is an abstract adapter that serves as the base class for most other CAPTCHA adapters. It provides mutators for specifying word length, session TTL, the session namespace object to use, and the session namespace class to use for persistence if you do not wish to use `Zend_Session_Namespace`. `Zend_Captcha_Word` encapsulates validation logic.

By default, the word length is 8 characters, the session timeout is 5 minutes, and `Zend_Session_Namespace` is used for persistence (using the namespace "`Zend_Form_Captcha_<captcha ID>`").

In addition to the methods required by the `Zend_Captcha_Adapter` interface, `Zend_Captcha_Word` exposes the following methods:

- `setWordLen($length)` and `getWordLen()` allow you to specify the length of the generated "word" in characters, and to retrieve the current value.

- `setTimeout($ttl)` and `getTimeout()` allow you to specify the time-to-live of the session token, and to retrieve the current value. `$ttl` should be specified in seconds.

- `setUseNumbers($numbers)` and `getUseNumbers()` allow you to specify if numbers will be considered as possible characters for the random work or only letters would be used.

- `setSessionClass($class)` and `getSessionClass()` allow you to specify an alternate `Zend_Session_Namespace` implementation to use to persist the CAPTCHA token and to retrieve the current value.

- `getId()` allows you to retrieve the current token identifier.

- `getWord()` allows you to retrieve the generated word to use with the CAPTCHA. It will generate the word for you if none has been generated yet.

- `setSession(Zend_Session_Namespace $session)` allows you to specify a session object to use for persisting the CAPTCHA token. `getSession()` allows you to retrieve the current session object.

All word CAPTCHAs allow you to pass an array of options to the constructor, or, alternately, pass them to `setOptions()`. You can also pass a `Zend_Config` object to `setConfig()`. By default, the wordLen, timeout, and sessionClass keys may all be used. Each concrete implementation may define additional keys or utilize the options in other ways.

`Zend_Captcha_Word` is an abstract class and may not be instantiated directly.

## Zend_Captcha_Dumb

The `Zend_Captch_Dumb` adapter is mostly self-descriptive. It provides a random string that must be typed in reverse to validate. As such, it's not a good CAPTCHA solution and should only be used for testing. It extends `Zend_Captcha_Word`.

## Zend_Captcha_Figlet

The `Zend_Captcha_Figlet` adapter utilizes `Zend_Text_Figlet` to present a figlet to the user.

Options passed to the constructor will also be passed to the `Zend_Text_Figlet` object. See the `Zend_Text_Figlet` documentation for details on what configuration options are available.

## Zend_Captcha_Image

The `Zend_Captcha_Image` adapter takes the generated word and renders it as an image, performing various skewing permutations to make it difficult to automatically decipher. It requires the GD extension compiled with TrueType or Freetype support. Currently, the `Zend_Captcha_Image` adapter can only generate PNG images.

`Zend_Captcha_Image` extends `Zend_Captcha_Word`, and additionally exposes the following methods:

- `setExpiration($expiration)` and `getExpiration()` allow you to specify a maximum lifetime the CAPTCHA image may reside on the filesystem. This is typically a longer than the session lifetime. Garbage collection is run periodically each time the CAPTCHA object is invoked, deleting all images that have expired. Expiration values should be specified in seconds.

- `setGcFreq($gcFreq)` and `getGcFreg()` allow you to specify how frequently garbage collection should run. Garbage collection will run every `1/$gcFreq` calls. The default is 100.

- `setFont($font)` and `getFont()` allow you to specify the font you will use. `$font` should be a fully qualified path to the font file. This value is required; the CAPTCHA will throw an exception during generation if the font file has not been specified.

- `setFontSize($fsize)` and `getFontSize()` allow you to specify the font size in pixels for generating the CAPTCHA. The default is 24px.

- `setHeight($height)` and `getHeight()` allow you to specify the height in pixels of the generated CAPTCHA image. The default is 50px.

- `setWidth($width)` and `getWidth()` allow you to specify the width in pixels of the generated CAPTCHA image. The default is 200px.

- `setImgDir($imgDir)` and `getImgDir()` allow you to specify the directory for storing CAPTCHA images. The default is "`./images/captcha/`", relative to the bootstrap script.

- `setImgUrl($imgUrl)` and `getImgUrl()` allow you to specify the relative path to a CAPTCHA image to use for HTML markup. The default is "`/images/captcha/`".

- `setSuffix($suffix)` and `getSuffix()` allow you to specify the filename suffix for the CAPTCHA image. The default is "`.png`". Note: changing this value will not change the type of the generated image.

- `setDotNoiseLevel($level)` and `getDotNoiseLevel()`, along with `setLineNoiseLevel($level)` and `getLineNoiseLevel()`, allow you to control how much "noise" in the form of random dots and lines the image would contain. Each unit of `$level` produces one random dot or line. The default is 100 dots and 5 lines. The noise is added twice - before and after the image distortion transformation.

All of the above options may be passed to the constructor by simply removing the 'set' method prefix and casting the initial letter to lowercase: "suffix", "height", "imgUrl", etc.

## Zend_Captcha_ReCaptcha

The `Zend_Captcha_ReCaptcha` adapter uses Zend_Service_ReCaptcha to generate and validate CAPTCHAs. It exposes the following methods:

- `setPrivKey($key)` and `getPrivKey()` allow you to specify the private key to use for the ReCaptcha service. This must be specified during construction, although it may be overridden at any point.

- `setPubKey($key)` and `getPubKey()` allow you to specify the public key to use with the ReCaptcha service. This must be specified during construction, although it may be overridden at any point.

- `setService(Zend_Service_ReCaptcha $service)` and `getService()` allow you to set and get the ReCaptcha service object.

- `isValid($value, $context = null)` validates the user's input against the ReCaptcha service. `$value` is an array with the following keys:

  - `recaptcha_challenge_field` - Value of the ReCaptcha widget's challenge field (hidden)

  - `recaptcha_response_field` - Value of the ReCaptcha widget's user input field