WordPress Snippet

function my_wp_nav_menu_add_custom_class( $classes, $item ) {
 if ( $item->ID== 25840 ) {
 $classes[]= "my_element";
 }
 return $classes;
}

add_filter( 'nav_menu_css_class', 'my_wp_nav_menu_add_custom_class', 10, 2 );