WP Nav menu add class

special_nav_class.php

//Filtering a Class in Navigation Menu Item
add_filter('nav_menu_css_class' , 'special_nav_class' , 10 , 2);
function special_nav_class($classes, $item){
     if(is_singular('post') && $item->title == 'Menu Item'){
             $classes[] = 'current-menu-item';
     }
     if(is_singular('post_type') && $item->title == 'Menu_Item'){
             $classes[] = 'current-menu-item';
     }
     return $classes;
}