WordPress Plugin Uninstallation

plugin-uninstallation-done-better.php

<?php
// Callback function for `register_uninstall_hook()`.
function myplugin_uninstall() {
  global $wpdb;
  
  // Check if we are on a Multisite or not.
  if ( is_multisite() ) {
    // Retrieve all site IDs from all networks (WordPress >= 4.6 provides easy to use functions for that).
    if ( function_exists( 'get_sites' ) ) {
      $site_ids = get_sites( array( 'fields' => 'ids' ) );
    } else {
      $site_ids = $wpdb->get_col( "SELECT blog_id FROM $wpdb->blogs;" );
    }
    
    // Uninstall the plugin for all these sites.
    foreach ( $site_ids as $site_id ) {
      switch_to_blog( $site_id );
      myplugin_uninstall_single_site();
      restore_current_blog();
    }
  } else {
    myplugin_uninstall_single_site();
  }
}
register_uninstall_hook( __FILE__, 'myplugin_uninstall' ); // __FILE__ is supposed to be the plugin's main file.