MarcusCJHartmann / MathCaptcha

a simple PHP-Class to generate Maths Captchas and display it as text or svg. No Serverside image rendering required.

MathsCaptcha

MathsCaptcha is a simple PHP Class for using captchas in php forms. It works by creating a simple maths task displayed as SVG. The correct answer is served as hashed value with the SVG and can be compared after form submition with user input by classown method.

The class

$captcha=new MathsCaptcha("+|-|x|:")  

The class-Constructor expects an optional maths operator for the Captcha.

Methods

MathsCaptcha::verify(input,hash)

Calculates the hashvalue from captcha input and compares it with given hash.

$captcha->getCaptchaJson()

Returns json-String with svg in field "_captcha_svg" and hash in "_captcha_hash"

$captcha->getCaptcha()

Echoes a complete HTML-Snippet with SVG-Captcha, hidden hash input named "_captcha_hash" and solution input named "_captcha_solution". Uses all following methods.

$captcha->getResultHash()

Returns the captcha result hash

$captcha->getMaths()

Returns the captcha task as plain letters.

$captcha->getSVGMaths

Returns the captcha task as SVG

Simple Code example

In your form:

$captcha=new MathsCaptcha(); 
$captcha->getCaptcha();

In your form validation:

if($_REQUEST&&$_REQUEST["_captcha_solution"]&&$_REQUEST["_captcha_hash"]){
    if(MathsCaptcha::verify($_REQUEST["_captcha_solution"],$_REQUEST["_captcha_hash"])){
    //PROCESS FORM
    }
}