假设您正在使用wp_nav_menu() 要显示导航，可以应用查找css类的walker：

$items_wrap  = \'<nav class="...">\';
$items_wrap .= \'<ul id="%1$s" class="%2$s">%3$s</ul>\';
$items_wrap .= \'</nav>\';

wp_nav_menu( array(
    \'container\'         => false,
    \'container_class\'   => false,
    \'menu_class\'        => \'...\',
    \'echo\'              => true,
    \'before\'            => \'\',
    \'after\'             => \'\',
    \'link_before\'       => \'\',
    \'link_after\'        => \'\',
    \'depth\'             => 0,
    \'theme_location\'    => \'...\',
    \'items_wrap\'        => $items_wrap,
    \'walker\'            => new Texas_Ranger(),
) );

然后需要将下面的walker类添加到functions.php 文件：

class Texas_Ranger extends Walker_Nav_Menu {

    /**
     * Building the List Item element
     * @param Referenced string $output
     * @param Post Object $item
     * @param int $depth
     * @param array $args
     * @return void
     */
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
        $indent         = ( $depth > 0 ? str_repeat( "\\t", $depth ) : \'\' );

        // Passed Classes
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;
        $class_names = esc_attr( implode( \' \', apply_filters( \'nav_menu_css_class\', array_filter( $classes ), $item ) ) );

        // build html
        $output .= $indent . \'<li id="nav-menu-item-\'. $item->ID . \'" class="\' . $class_names . \'">\';

        // If \'noLink\' exists in classes, don\'t HTML anchor tag.
        if( in_array( \'noLink\', $classes ) ) {

            $item_output = apply_filters( \'the_title\', $item->title, $item->ID );

        } else {

            // link attributes
            $attributes  = ! empty( $item->attr_title ) ? \' title="\'  . esc_attr( $item->attr_title ) .\'"\' : \'\';
            $attributes .= ! empty( $item->target )     ? \' target="\' . esc_attr( $item->target     ) .\'"\' : \'\';
            $attributes .= ! empty( $item->xfn )        ? \' rel="\'    . esc_attr( $item->xfn        ) .\'"\' : \'\';
            $attributes .= ! empty( $item->url )        ? \' href="\'   . esc_attr( $item->url        ) .\'"\' : \'\';
            $attributes .= \' class="menu-link \' . ( $depth > 0 ? \'sub-menu-link\' : \'main-menu-link\' ) . \'"\';

            $item_output = sprintf( \'%1$s<a%2$s>%3$s%4$s%5$s</a>%6$s\',
                $args->before,
                $attributes,
                $args->link_before,
                apply_filters( \'the_title\', $item->title, $item->ID ),
                $args->link_after,
                $args->after
            );
        }

        // build html
        $output .= apply_filters( \'walker_nav_menu_start_el\', $item_output, $item, $depth, $args );
    }
}

最后一步是登录WordPress，导航到Appearance -> Menus 在右上角，单击Screen Options 并确保选中“CSS类”：