uninstall.php

<?php
if ( ! defined( 'ABSPATH' ) && ! defined( 'WP_UNINSTALL_PLUGIN' ) ) {
	exit(); // Make sure not to call this file directly.
}

// Is Subscribe2 HTML active.
if ( is_plugin_active( 'subscribe2_html/subscribe2.php' ) ) {
	return;
}

$s2_mu = false;

// Is this WordPressMU or not?
if ( isset( $wpmu_version ) || ( isset( $wp_version ) && strpos( $wp_version, 'wordpress-mu' ) ) ) {
	$s2_mu = true;
}

if ( function_exists( 'is_multisite' ) && is_multisite() ) {
	$s2_mu = true;
}

if ( $s2_mu ) {
	global $wpdb;

	$blogs = $wpdb->get_col( "SELECT blog_id FROM {$wpdb->blogs}" );
	foreach ( $blogs as $blog ) {
		switch_to_blog( $blog );
		s2_uninstall();
		restore_current_blog();
	}
} else {
	s2_uninstall();
}

function s2_uninstall() {
	global $wpdb;

	// Delete entry from wp_options table.
	delete_option( 'subscribe2_options' );
	// Delete legacy entry from wp-options table.
	delete_option( 's2_future_posts' );

	// Remove and scheduled events.
	wp_clear_scheduled_hook( 's2_digest_cron' );

	// Delete usermeta data for registered users. Use LIKE and % wildcard as meta_key names are prepended on WPMU.
	// And s2_cat is appended with category ID integer.
	$wpdb->query( "DELETE from $wpdb->usermeta WHERE meta_key LIKE '%s2_cat%'" );
	$wpdb->query( "DELETE from $wpdb->usermeta WHERE meta_key LIKE '%s2_subscribed'" );
	$wpdb->query( "DELETE from $wpdb->usermeta WHERE meta_key LIKE '%s2_format'" );
	$wpdb->query( "DELETE from $wpdb->usermeta WHERE meta_key LIKE '%s2_autosub'" );
	// Delete any postmeta data that suppressed notifications.
	$wpdb->query( "DELETE from $wpdb->postmeta WHERE meta_key = 's2mail'" );

	// drop the subscribe2 table
	$wpdb->query( "DROP TABLE IF EXISTS {$wpdb->prefix}subscribe2" );
}