Add extra classes to ‘current menu item’

Some of my previous projects involved re-developing HTML-built websites in to bespoke WordPress themes, majority of these sites being built using Bootstrap.

When it came to creating the menu, I found it easier to just add the ‘active’ class to the ‘current menu item’ rather than amending the Bootstrap CSS to apply active styles to .current-menu-item rather than .active.

add_filter('nav_menu_css_class' , 'active_nav_class' , 10 , 2);
function active_nav_class($classes, $item){
    if( in_array('current-menu-item', $classes) ){
        $classes[] = 'active ';
    }
    return $classes;
}