Wednesday, October 22, 2014

Walker Function in WordPress menu function(wp nav menu)

Displays a navigation menu created in the Appearance → Menus panel.

Usages


<?php

$defaults = array(
 'theme_location'  => '',
 'menu'            => '',
 'container'       => 'div',
 'container_class' => '',
 'container_id'    => '',
 'menu_class'      => 'menu',
 'menu_id'         => '',
 'echo'            => true,
 'fallback_cb'     => 'wp_page_menu',
 'before'          => '',
 'after'           => '',
 'link_before'     => '',
 'link_after'      => '',
 'items_wrap'      => '<ul id="%1$s" class="%2$s">%3$s</ul>',
 'depth'           => 0,
 'walker'          => ''
);

wp_nav_menu( $defaults );

?>

On the above example there are one option(Walker) in the default array. In this post I will write about the walker menu how to use this option.


<?php

class headerTopFirstMenuWalkerMob extends Walker_Nav_Menu
{
    public function start_lvl( &$output, $depth = 0, $args = array() ) {
  $indent = str_repeat("\t", $depth);
  $output .= "\n$indent<ul class=\"mob_sub_nav\">\n";
 }

 /**
  * Ends the list of after the elements are added.
  *
  * @see Walker::end_lvl()
  *
  * @since 3.0.0
  *
  * @param string $output Passed by reference. Used to append additional content.
  * @param int    $depth  Depth of menu item. Used for padding.
  * @param array  $args   An array of arguments. @see wp_nav_menu()
  */
 public function end_lvl( &$output, $depth = 0, $args = array() ) {
  $indent = str_repeat("\t", $depth);
  $output .= "$indent</ul>\n";
 }

 /**
  * Start the element output.
  *
  * @see Walker::start_el()
  *
  * @since 3.0.0
  *
  * @param string $output Passed by reference. Used to append additional content.
  * @param object $item   Menu item data object.
  * @param int    $depth  Depth of menu item. Used for padding.
  * @param array  $args   An array of arguments. @see wp_nav_menu()
  * @param int    $id     Current item ID.
  */
 public function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
  $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';

  $classes = empty( $item->classes ) ? array() : (array) $item->classes;
  $classes[] = 'menu-item-' . $item->ID;

  /**
   * Filter the CSS class(es) applied to a menu item's <li>.
   *
   * @since 3.0.0
   *
   * @see wp_nav_menu()
   *
   * @param array  $classes The CSS classes that are applied to the menu item's <li>.
   * @param object $item    The current menu item.
   * @param array  $args    An array of wp_nav_menu() arguments.
   */
  $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );
  $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';

  /**
   * Filter the ID applied to a menu item's <li>.
   *
   * @since 3.0.1
   *
   * @see wp_nav_menu()
   *
   * @param string $menu_id The ID that is applied to the menu item's <li>.
   * @param object $item    The current menu item.
   * @param array  $args    An array of wp_nav_menu() arguments.
   */
  $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );
  $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';

  $output .= $indent . '<li>';

  $atts = array();
  $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';
  $atts['target'] = ! empty( $item->target )     ? $item->target     : '';
  $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';
  $atts['href']   = ! empty( $item->url )        ? $item->url        : '';

  /**
   * Filter the HTML attributes applied to a menu item's <a>.
   *
   * @since 3.6.0
   *
   * @see wp_nav_menu()
   *
   * @param array $atts {
   *     The HTML attributes applied to the menu item's <a>, empty strings are ignored.
   *
   *     @type string $title  Title attribute.
   *     @type string $target Target attribute.
   *     @type string $rel    The rel attribute.
   *     @type string $href   The href attribute.
   * }
   * @param object $item The current menu item.
   * @param array  $args An array of wp_nav_menu() arguments.
   */
  $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );

  $attributes = '';
  foreach ( $atts as $attr => $value ) {
   if ( ! empty( $value ) ) {
    $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );
    $attributes .= ' ' . $attr . '="' . $value . '"';
   }
  }

  $item_output = $args->before;
  $item_output .= '<a'. $attributes .'>';
  /** This filter is documented in wp-includes/post-template.php */
  $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;
  $item_output .= '</a>';
  $item_output .= $args->after;

  /**
   * Filter a menu item's starting output.
   *
   * The menu item's starting output only includes $args->before, the opening <a>,
   * the menu item's title, the closing </a>, and $args->after. Currently, there is
   * no filter for modifying the opening and closing <li> for a menu item.
   *
   * @since 3.0.0
   *
   * @see wp_nav_menu()
   *
   * @param string $item_output The menu item's starting HTML output.
   * @param object $item        Menu item data object.
   * @param int    $depth       Depth of menu item. Used for padding.
   * @param array  $args        An array of wp_nav_menu() arguments.
   */
  $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
 }

 /**
  * Ends the element output, if needed.
  *
  * @see Walker::end_el()
  *
  * @since 3.0.0
  *
  * @param string $output Passed by reference. Used to append additional content.
  * @param object $item   Page data object. Not used.
  * @param int    $depth  Depth of page. Not Used.
  * @param array  $args   An array of arguments. @see wp_nav_menu()
  */
 public function end_el( &$output, $item, $depth = 0, $args = array() ) {
  $output .= "</li>\n";
 }

}

Use the bellow code instead of the wp_nav_menu and see the magic. Most important you could change into the walker and give your design or layout as you want.

$defaults = array(
 'theme_location'  => '',
 'menu'            => '',
 'container'       => 'div',
 'container_class' => '',
 'container_id'    => '',
 'menu_class'      => 'menu',
 'menu_id'         => '',
 'echo'            => true,
 'fallback_cb'     => 'wp_page_menu',
 'before'          => '',
 'after'           => '',
 'link_before'     => '',
 'link_after'      => '',
 'items_wrap'      => '<ul id="%1$s" class="%2$s">%3$s</ul>',
 'depth'           => 0,
 'walker'          => new headerTopFirstMenuWalkerMob()  
);

wp_nav_menu( $defaults ); 

?>