function remove_dashboard_widgets(){
    remove_meta_box('dashboard_recent_comments', 'dashboard', 'normal'); // Recent Comments
    remove_meta_box('dashboard_incoming_links', 'dashboard', 'normal');  // Incoming Links
    remove_meta_box('dashboard_plugins', 'dashboard', 'normal');   // Plugins
    remove_meta_box('dashboard_quick_press', 'dashboard', 'side');  // Quick Press
    remove_meta_box('dashboard_recent_drafts', 'dashboard', 'side');  // Recent Drafts
    remove_meta_box('dashboard_primary', 'dashboard', 'side');   // WordPress blog
    remove_meta_box('dashboard_secondary', 'dashboard', 'side');   // Other WordPress News
// use 'dashboard-network' as the second parameter to remove widgets from a network dashboard.
}
add_action('wp_dashboard_setup', 'remove_dashboard_widgets');

Wordpress

Remove dashboard widgets

PHP