need help w/captcha

[12Strings]

I need help with this Captcha code. when I try it, all I get is code,
starting with

"captcha_varname='$captcha_var_name';" through "?>"

It's like my Php wasn't working but I've confirmed it is. I'm hoping

someone will tell me why. Following is my code COPIED FROM ONLINE:

<?PHP
// simple-captcha.php
class FGSimpleCaptcha extends FG_CaptchaHandler;
 {
    var $error_str;
    var $captcha_varname;
    var $uniquekey;

function FGSimpleCaptcha($captcha_var_name)
 {
        $this->captcha_varname='$captcha_var_name'; // ?

    $this->uniquekey='abc12fghijkl34mno;
    }
/*Add more simple questions here.*/
function GetSimpleCaptcha()
 {
        $arrQuestions = array(
"Which of sock, library, cake or red is a color? "=>"red",
"Enter the number thirteen thousand three hundred and sixty eight in 

digits: "=>"13,368");        

    $question = array_rand($arrQuestions);
    $answer = $arrQuestions[$question];

    $_SESSION['FGCF_Captcha_Answer'] = $this->Md5CaptchaAnswer

($answer);

 return $question;
 }
    function SetFormKey($key)
    { $this->uniquekey = $key; }
    function GetKey()
    { return $this->uniquekey; }
    function Validate()
 {
        $ret=false;
        if(empty($_POST[$this->captcha_varname]))
 {
            $this->error_str = "Please answer the anti-spam question";
            $ret = false;
 }
        else
 {

        $scaptcha = trim($_POST[$this->captcha_varname]);

        $scaptcha = strtolower($scaptcha);

        $user_answer = $this->Md5CaptchaAnswer($scaptcha);

        if($user_answer != $_SESSION['FGCF_Captcha_Answer'])
 {
                $this->error_str = "Failed the anti-spam check!";
                $ret = false;
 }
            else
            { $ret = true; }
 }
//else
        return $ret;
 }
    function Md5CaptchaAnswer($answer)
 { return md5($this->GetKey().$answer); }
    function GetError()
    { return $this->error_str; }
 }
?>