聪明的验证码不起作用

I have this problem with smarty, I tried to add a captcha in smarty but I can't see the way of make it work, basically the error comes when i try to show the captcha image, in a normal php file I could embed this php script:

<?php 
    $SampleCaptcha = new Captcha("SampleCaptcha");
    $SampleCaptcha->UserInputID = "CaptchaCode";
    echo $SampleCaptcha->Html();
?>

But for smarty I did this:

$SampleCaptcha = new Captcha("SampleCaptcha");
$SampleCaptcha->UserInputID = "CaptchaCode";
$captcha=$SampleCaptcha->Html();
$sy->assign('captcha', $captcha);

The think is that the variable captcha does print the whole html to show the captcha but when it prints the image attr src it does it in php still.

<img alt="CAPTCHA" src="botdetect.php?get=image&amp;c=samplecaptcha&amp;t=da491a96235a0d9f5fbeb0d7c0accc89" id="SampleCaptcha_CaptchaImage" class="LBD_CaptchaImage">

I tried to use a smarty plugin function but it does the same.

Any expert in smarty may know the answer.

Many thanks.

Try this. It may help you as this site has good examples across different platforms.