//How to redirect logins based upon a variable!

//This function returns a redirect location based upon a variable.
function overHere() {
    //Declare variables.
    $variable = true;

    if (!$variable) {
        $redirect_to = "/here";
        return $redirect_to;
    } else {
        $redirect_to = "/there";
        return $redirect_to;
    }
}

//Add that filter with eleven priority!
add_filter('login_redirect', 'overHere', 11);