Redirect Away if not logged in and redirect back

functions.php

<?php
function si_redirect_if_not_logged_in() {
	$url = get_permalink( $invoice_id );
	if ( !is_user_logged_in() ) {
		wp_redirect( home_url() . '/login/?redirect_to=' . $url . '&reauth=1');
		exit();
	}
}
//
add_action( 'pre_si_invoice_view', 'si_redirect_if_not_logged_in' );
add_action( 'pre_si_estimate_view', 'si_redirect_if_not_logged_in' );
//