WordPress分类页面显示该分类置顶文章的教程

如果仅仅在首页展示分类文章，那就比较局限了，有时候访客直接访问的是分类页面，如果在这个页面看到置顶的文章，用户体验还是不错的。

默认WordPress仅在首页显示置顶文章，那么要在分类页面显示该分类置顶文章，如何实现呢？可以尝试使用下面的代码。

将代码添加到当前主题函数模板 functions.php 中：

class StickyInCategory {
  /**
   * A reference to an instance of this class.
   */
  private static $instance;
 
  /**
   * The array of categories that will have sticky posts moved to the top.
   */
  protected $categories;
    
  /**
   * Returns an instance of this class. 
   */
  public static function get_instance() {
 
    if ( null == self::$instance ) {
      self::$instance = new StickyInCategory();
    }
 
    return self::$instance;
 
  }
 
  /**
   * Initializes the plugin by setting filters and administration functions.
   */
  private function __construct() {
 
    $this->categories = array();
 
    // Filter retrieved posts
    add_filter(  'the_posts', array( $this, 'prepend_sticky_posts' ), 10, 2 );
    
    // Set the 'sticky' class
    add_filter( 'post_class', array( $this, 'set_sticky_post_class' ), 10, 3 );
  }
 
  /**
   * Move sticky posts to the top of the archive listing.
   */
  public function prepend_sticky_posts( $posts, $query ) {
 
    if ( !is_admin() && is_main_query() ) {
      
      // Hook to initialise the categories if none specified.
      if ( empty( $this->categories ) ) {
        $this->categories = apply_filters( 'sia_sticky_categories', $this->categories );
      }
 
      // Only continue if we are viewing a category archive.
      if ( array_key_exists( 'category_name', $query->query_vars ) ) {
        $category_matched = false;
        if ( empty( $this->categories ) ) {
          // If no categories were supplied by the apply_filters() then operate on all categories.
          $category_matched = true;
        }
        else {
          // Check whether the current category is in the list.
          $category_matched = in_array( $query->query_vars['category_name'], $this->categories );
        }
 
        if ( $category_matched ) {
          // Copied from the bottom of WP_Query::get_posts() in wp-includes/class-wp-query.php
          $sticky_posts = get_option( 'sticky_posts' );
          $num_posts = count( $posts );
          $sticky_offset = 0;
          // Loop over posts and relocate stickies to the front.
          for ( $i = 0; $i < $num_posts; $i++ ) {
            if ( in_array( $posts[ $i ]->ID, $sticky_posts ) ) {
              $sticky_post = $posts[ $i ];
              // Remove sticky from current position
              array_splice( $posts, $i, 1 );
              // Move to front, after other stickies
              array_splice( $posts, $sticky_offset, 0, array( $sticky_post ) );
              // Increment the sticky offset. The next sticky will be placed at this offset.
              $sticky_offset++;
              // Remove post from sticky posts array
              $offset = array_search( $sticky_post->ID, $sticky_posts );
              unset( $sticky_posts[ $offset ] );
            }
          }
        }
      }
    }
    return $posts;
  }
 
  /**
   * Set the 'sticky' post class. get_post_class() only does it on the home page.
   */
  public function set_sticky_post_class( $classes, $class, $post_ID ) {
    
    // TODO: Consider whether to reference $this->categories.
    if ( is_archive() && is_sticky( $post_ID ) ) {
      $classes[] = 'sticky';
    }
    return $classes;
  }
}
 
add_action( 'after_setup_theme', array( 'StickyInCategory', 'get_instance' ) );