Super simple form Captcha using RainCaptcha

Super simple form Captcha using RainCaptcha

Dec 9, 2013·

1 min read

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RainCaptcha is simple to use CAPTCHA for forms, it helps prevent spam submissions by creating images on the fly with embedded text. It can generate an URL to display a CAPTCHA validation image served by the RainCaptcha service.

The class can also send a request to RainCaptcha API to verify if the text that the user entered matches the text in the CAPTCHA image.

RainCaptcha is a CAPTCHA class that does not require any image processing extensions (GD, ImageMagick, etc). CAPTCHA was developed to be readable by humans and resistant to OCR software. It generates black-and-white images with 5 distorted letters on them and noise. Its checking algorithm is case-insensitive.<

Rather then writing a full class to do the heavy lifting make use of the free PHP class already available at

To use the class include it on the page then create a new instance, this can then be used to generate a captcha image using ->getImage()

<?php $rainCaptcha = new RainCaptcha(); ?>
<img id="captchaImage" src="<?php echo $rainCaptcha->getImage(); ?>" />
<input name="captcha" type="text" />
<button type="button" class='btn btn-danger' onclick="document.getElementById('captchaImage').src = 
'<?php echo $rainCaptcha->getImage(); ?>&amp;morerandom=' + Math.floor(Math.random() * 10000);"><span class="icon icon-refresh"></span></button>

To check if a user's input matches the captcha

$rainCaptcha = new RainCaptcha();
    die('You have not passed the CAPTCHA test!');