variables name and sitetitle in email subjects

[frommarcq +]

Hi,
I want to display the fields {$name} and {$sitetitle} in subjects of html/text emails, but if If I do that :

PHP Code:

{assign var='subject' value='message from {$name} on the website {$sitetitle}'} 


or with

PHP Code:

{assign var='subject' value='message from $name on the website $sitetitle'} 


An error occurs.

Could you "tell me the way" ?

Regards

Pascal