CODE EXAMPLE FOR PHP

wordpress notice

// for success
<div class="notice notice-success is-dismissible">
        <p><?php _e( 'Done!', 'sample-text-domain' ); ?></p>
</div>
  
// for error  
<div class="notice notice-error is-dismissible ">
        <p><?php _e( 'Error message here!', 'sample-text-domain' ); ?></p>
</div>