How to optimize if-statemnts php?

How to optimize PHP?? I'd like to optimize this code with if-statements in PHP.

$head =  make_number($_GET['id']);
if(isset($head)){
    echo $head;
}
else {
    $head =  make_number($_GET['id']);
    if(isset($head)){
        echo $head;
    }
    else {
        $head =  make_number($_GET['url']);
        if(isset($head)){
            echo $head;
        }
    }
}