Information about the CAPTCHA and inner workings
Text_CAPTCHA provides information
about the CAPTCHA and makes its inner workings accessible
using several functions defined in the base
class; the specific implementation of them is up to
init() is used to initialize the CAPTCHA and provide
further information, like Image_Text
_createCAPTCHA() generates the CAPTCHA, but is called
internally by init().
getPhrase() returns the CAPTCHA's phrase.
_createPhrase() creates a phrase for the CAPTCHA,
but is used internally.
getCAPTCHA() returns the CAPTCHA, the format used
depends on the driver implementation.