Nav Walker Class for Wordpress Bootstrap Dropdown Menu

//this class will output the structure of the bootstrap nav menu.. we can also customize the walker class for our personal use.
class Primary_Walker_Nav_Menu extends Walker_Nav_Menu {
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
        if ( array_search( 'menu-item-has-children', $item->classes ) ) {
            $output .= sprintf( "\n<li class='dropdown %s'><a href='%s' class=\"dropdown-toggle\" data-toggle=\"dropdown\" >%s</a>\n", ( array_search( 'current-menu-item', $item->classes ) || array_search( 'current-page-parent', $item->classes ) ) ? 'active' : '', $item->url, $item->title );
        } else {
            $output .= sprintf( "\n<li %s><a href='%s'>%s</a>\n", ( array_search( 'current-menu-item', $item->classes) ) ? ' class="active"' : '', $item->url, $item->title );
        }
    }

    function start_lvl( &$output, $depth ) {
        $indent = str_repeat( "\t", $depth );
        $output .= "\n$indent<ul class=\"dropdown-menu\" role=\"menu\">\n";
    }
}