How To Convert Bootstrap Menu In WordPress

We are going to make WordPress menu int bootstrap menu by walker class. first define class and called walker following code in function.php file

class submenu_wrapper extends Walker_Nav_Menu {
// add classes to ul sub-menus
function start_lvl( &$output, $depth = 0, $args = array() ) {
// depth dependent classes
$indent = ( $depth > 0 ? str_repeat( "\t", $depth ) : '' ); // code indent
$display_depth = ( $depth + 1); // because it counts the first submenu as 0
$classes = array(
/* 'dropdown-menu left-1'*/
'dropdown-menu'
);
$class_names = implode( ' ', $classes );   
 // build html
    if ($display_depth == 1) {
        $output .= "\n" . $indent . '<ul class="' . $class_names . '">' . "\n";
    } else {
        $output .= "\n" . $indent . '<ul class="' . $class_names . '">' . "\n";
    }
}
}

After the extending walker class, we will add classes and attribute in anchor tag by “nav_menu_link_attributes” Filter. for a you have to use it as per following code.

add_filter( 'nav_menu_link_attributes', 'anchor_menu_add_class', 10, 4 );    
function anchor_menu_add_class( $atts, $item, $args ,$depth=0) {
        if ($args->walker->has_children==1 && $depth === 0 ) {
          $atts['href']          = ! empty( $item->url ) ? $item->url : '';
          $atts['data-toggle']   = 'dropdown';
          $atts['class']         = 'dropdown-toggle';
          $atts['aria-haspopup']    = 'true';
          $atts['aria-expanded']='false';
        } elseif($depth === 0) {
            $atts['href'] = ! empty( $item->url ) ? $item->url : '';
            $atts['class']         = '';
        } elseif($depth === 1) {
          $atts['href'] = ! empty( $item->url ) ? $item->url : '';
          $atts['class']         = 'dropdown-item';
        }
        /*if($depth === 0) {
            $atts['href'] = ! empty( $item->url ) ? $item->url : '';
            $atts['class']         = 'nav-link';
        }elseif ($args->walker->has_children==1 && $depth === 0 ) {
          $atts['href']          = ! empty( $item->url ) ? $item->url : '';
          $atts['data-toggle']   = 'dropdown';
          $atts['class']         = 'nav-link dropdown-toggle';
          $atts['aria-haspopup']    = 'true';
          $atts['aria-expanded']='false';
        } elseif($depth === 1) {
          $atts['href'] = ! empty( $item->url ) ? $item->url : '';
          $atts['class']         = 'dropdown-item';
        }*/
       // print_r($args->walker->has_children);
        //echo "<pre>";
       // print_r($item);
        //die;
        return $atts;
    }

Calling walker In header.php

<?php 
echo wp_nav_menu(array('menu'=>'Home Menu','menu_class'=>'navbar-nav ml-auto','walker'=>new submenu_wrapper,'container'=>false)); 
?>

Add Active class in wordpress menu by hook