Add a custom dashboard widget to WordPress

function custom_dashboard_widget() {
    wp_add_dashboard_widget( 'custom_dashboard_widget', 'Custom Dashboard Widget', 'custom_dashboard_widget_function' );
}
add_action( 'wp_dashboard_setup', 'custom_dashboard_widget' );

function custom_dashboard_widget_function() {
  // custom dashboard widget function code goes here
 $widget_content = '<h3>I am a new dashboard widget</h3><p>Customize me!</p>';
 return $widget_content;
}