什么是使用php执行头的正确代码

I have this line in my execution script

$Headers = "From: ".$_POST['fname']." <support@domain.com> 
" . 

and it works fine.

I have tried in several ways to call up the user email address to replace support@... but all my effort failed.

I have tried this code

$Headers = "From: ".$_POST['fname']." <".$_POST['email']."> 
" .