Creates a CAPTCHA image in PHP, which displays 5 numbers stored in a session.

CAPTCHA s are used to prevent automated software from performing actions which degrade the quality of service of a given system, whether due to abuse or resource expenditure. Creates a CAPTCHA image in PHP, which displays 5 numbers. The code is stored in a session variable ... then, the user must enter the code correctly. Can be used on registration forms, login forms, etc.