code: public function validate()
  	{
  		if (!isset($_POST[$this->strCaptchaKey]) || !\in_array(Input::post($this->strCaptchaKey.'_hash'), $this->generateHashes((int) Input::post($this->strCaptchaKey)), true) || (isset($_POST[$this->strCaptchaKey.'_name']) && Input::post($this->strCaptchaKey.'_name')))
  		{
  			$this->class = 'error';
  			$this->addError($GLOBALS['TL_LANG']['ERR']['captcha']);
  		}
  	}
docs: Validate the input and set the value