PhpCaptcha::GenerateCode PHP Method

    function GenerateCode()
    {
        // reset code
        $this->sCode = '';
        // loop through and generate the code letter by letter
        for ($i = 0; $i < $this->iNumChars; $i++) {
            if (count($this->aCharSet) > 0) {
                // select random character and add to code string
                $this->sCode .= $this->aCharSet[array_rand($this->aCharSet)];
            } else {
                // select random character and add to code string
                $this->sCode .= chr(rand(65, 90));
            }
        }
        // save code in session variable
        if ($this->bCaseInsensitive) {
            $_SESSION[CAPTCHA_SESSION_ID] = strtoupper($this->sCode);
        } else {
            $_SESSION[CAPTCHA_SESSION_ID] = $this->sCode;
        }
    }