Plugin won’t activate

From stackoverflow: https://stackoverflow.com/questions/2450510/redirect-after-plugin-activation

register_activation_hook(__FILE__, 'my_plugin_activate');
add_action('admin_init', 'my_plugin_redirect');

function my_plugin_activate() {
    add_option('my_plugin_do_activation_redirect', true);
}

function my_plugin_redirect() {
    if (get_option('my_plugin_do_activation_redirect', false)) {
        delete_option('my_plugin_do_activation_redirect');
        wp_redirect(MY_PLUGIN_SETTINGS_URL);
    }
}