diff -r 7b1b88e27a20 -r 48c4eec2b7e6 wp/wp-admin/network/site-users.php
--- a/wp/wp-admin/network/site-users.php	Thu Sep 29 08:06:27 2022 +0200
+++ b/wp/wp-admin/network/site-users.php	Fri Sep 05 18:40:08 2025 +0200
@@ -213,7 +213,8 @@
 	wp_enqueue_script( 'user-suggest' );
 }
 
-require_once ABSPATH . 'wp-admin/admin-header.php'; ?>
+require_once ABSPATH . 'wp-admin/admin-header.php';
+?>
 
 <script type="text/javascript">
 var current_site_id = <?php echo absint( $id ); ?>;
@@ -233,41 +234,57 @@
 );
 
 if ( isset( $_GET['update'] ) ) :
+	$message = '';
+	$type    = 'error';
+
 	switch ( $_GET['update'] ) {
 		case 'adduser':
-			echo '<div id="message" class="updated notice is-dismissible"><p>' . __( 'User added.' ) . '</p></div>';
+			$type    = 'success';
+			$message = __( 'User added.' );
 			break;
 		case 'err_add_member':
-			echo '<div id="message" class="error notice is-dismissible"><p>' . __( 'User is already a member of this site.' ) . '</p></div>';
+			$message = __( 'User is already a member of this site.' );
 			break;
 		case 'err_add_fail':
-			echo '<div id="message" class="error notice is-dismissible"><p>' . __( 'User could not be added to this site.' ) . '</p></div>';
+			$message = __( 'User could not be added to this site.' );
 			break;
 		case 'err_add_notfound':
-			echo '<div id="message" class="error notice is-dismissible"><p>' . __( 'Enter the username of an existing user.' ) . '</p></div>';
+			$message = __( 'Enter the username of an existing user.' );
 			break;
 		case 'promote':
-			echo '<div id="message" class="updated notice is-dismissible"><p>' . __( 'Changed roles.' ) . '</p></div>';
+			$type    = 'success';
+			$message = __( 'Changed roles.' );
 			break;
 		case 'err_promote':
-			echo '<div id="message" class="error notice is-dismissible"><p>' . __( 'Select a user to change role.' ) . '</p></div>';
+			$message = __( 'Select a user to change role.' );
 			break;
 		case 'remove':
-			echo '<div id="message" class="updated notice is-dismissible"><p>' . __( 'User removed from this site.' ) . '</p></div>';
+			$type    = 'success';
+			$message = __( 'User removed from this site.' );
 			break;
 		case 'err_remove':
-			echo '<div id="message" class="error notice is-dismissible"><p>' . __( 'Select a user to remove.' ) . '</p></div>';
+			$message = __( 'Select a user to remove.' );
 			break;
 		case 'newuser':
-			echo '<div id="message" class="updated notice is-dismissible"><p>' . __( 'User created.' ) . '</p></div>';
+			$type    = 'success';
+			$message = __( 'User created.' );
 			break;
 		case 'err_new':
-			echo '<div id="message" class="error notice is-dismissible"><p>' . __( 'Enter the username and email.' ) . '</p></div>';
+			$message = __( 'Enter the username and email.' );
 			break;
 		case 'err_new_dup':
-			echo '<div id="message" class="error notice is-dismissible"><p>' . __( 'Duplicated username or email address.' ) . '</p></div>';
+			$message = __( 'Duplicated username or email address.' );
 			break;
 	}
+
+	wp_admin_notice(
+		$message,
+		array(
+			'type'        => $type,
+			'dismissible' => true,
+			'id'          => 'message',
+		)
+	);
 endif;
 ?>