How to Redirect After Plugin Activation

membership-plus.php

<?php
/**
 * Plugin Name:       Memberships Plus
 * Plugin URI:        https://dlxplugins.com/plugins/
 * Description:       A Pro membership plugin.
 * Version:           1.0.0
 * Requires at least: 5.8
 * Requires PHP:      7.2
 * Author:            DLX Plugins
 * Author URI:        https://dlxplugins.com
 * License:           GPL v2 or later
 * License URI:       https://www.gnu.org/licenses/gpl-2.0.html
 *
 * @package MembershipsPlus
 */

/**
 * Callback for adding an admin menu.
 */
function memberships_plus_add_admin_menu() {
	add_options_page(
		'Memberships Plus',
		'Memberships Plus',
		'manage_options',
		'memberships-plus',
		'memberships_plus_options_page'
	);
}
add_action( 'admin_menu', 'memberships_plus_add_admin_menu' );

/**
 * Callback for the admin panel options.
 */
function memberships_plus_options_page() {
	?>
	<div class="wrap">
		<h1>Memberships Plus</h1>
		<p>Welcome to Memberships Plus.</p>
	</div>
	<?php
}

register_activation_hook( __FILE__, 'memberships_plus_plugin_activate' );
/**
 * Add an option upon activation to read in later when redirecting.
 */
function memberships_plus_plugin_activate() {
	if ( memberships_plus_can_redirect_on_activation() ) {
		add_option( 'memberships_plus_plugin_do_activation_redirect', sanitize_text_field( __FILE__ ) );
	}
}

/**
 * Determine if a user can be redirected or not.
 *
 * @return true if the user can be redirected. false if not.
 */
function memberships_plus_can_redirect_on_activation() {
	// If plugin is activated in network admin options, skip redirect.
	if ( is_network_admin() ) {
		return false;
	}

	// Skip redirect if WP_DEBUG is enabled.
	if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
		return false;
	}

	// Determine if multi-activation is enabled.
	$maybe_multi = filter_input( INPUT_GET, 'activate-multi', FILTER_VALIDATE_BOOLEAN );
	if ( $maybe_multi ) {
		return false;
	}

	// All is well. Can redirect.
	return true;
}

add_action( 'admin_init', 'memberships_plus_plugin_activate_redirect' );
/**
 * Redirect a user to the admin panel after activation.
 */
function memberships_plus_plugin_activate_redirect() {
	if ( memberships_plus_can_redirect_on_activation() && is_admin() ) {
		// Read in option value.
		if ( __FILE__ === get_option( 'memberships_plus_plugin_do_activation_redirect' ) ) {

			// Delete option value so no more redirects.
			delete_option( 'memberships_plus_plugin_do_activation_redirect' );

			// Get redirect URL.
			$redirect_url = admin_url( 'options-general.php?page=memberships-plus' );
			wp_safe_redirect(
				esc_url( $redirect_url )
			);
			exit;
		}
	}
}