how to get variabe name in given situatin

I'm trying to get variable name in given situation. I'm using Laravel model to call specific template in a table

Example:

$user_name="raza";
$site="mysite.com";
$template=Template::find($id);
$res=template->body;
echo $res;

Output is :

"hi $user_name welcome to $site"

Required Output:

"hi raza welcome to mysite.com"

via Chebli Mohamed