echo "<option value='".$fv."'>".$fv."</option>";
can be more simply written as:
echo "<option value='$fv'>$fv</option>";
php is a server-side language - you need to get the value to the server to map it into a php symbol.
Now, for your question, getting the value from the
client side to the
server side will take use of either a <form> with your select inside, and the value will turn up in $_REQUEST array on the server side (target should be .php) when the form is submitted.
Alternatively, you can use AJAX to send the value to the server when some event of your choosing occurs - without modifying the current page on the user side if you don't want to. This route requires javaScript.