WordPress代码实现相关文章的几种方法

<ul id="xxx">
    <li>* <a title="文章标题1" rel="bookmark" href="文章链接1">文章标题1</a></li>
    <li>* <a title="文章标题2" rel="bookmark" href="文章链接2">文章标题2</a></li>
    ......
</ul>

<ul id="tags_related">
<?php
global $post;
$post_tags = wp_get_post_tags($post->ID);
if ($post_tags) {
  foreach ($post_tags as $tag) {
    // 获取标签列表
    $tag_list[] .= $tag->term_id;
  }

  // 随机获取标签列表中的一个标签
  $post_tag = $tag_list[ mt_rand(0, count($tag_list) - 1) ];

  // 该方法使用 query_posts() 函数来调用相关文章，以下是参数列表
  $args = array(
        'tag__in' => array($post_tag),
        'category__not_in' => array(NULL),  // 不包括的分类ID
        'post__not_in' => array($post->ID),
        'showposts' => 6,				            // 显示相关文章数量
        'caller_get_posts' => 1
    );
  query_posts($args);

  if (have_posts()) {
    while (have_posts()) {
      the_post(); update_post_caches($posts); ?>
    <li>* <a href="<?php the_permalink(); ?>" rel="bookmark" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a></li>
<?php
    }
  }
  else {
    echo '<li>* 暂无相关文章</li>';
  }
  wp_reset_query(); 
}
else {
  echo '<li>* 暂无相关文章</li>';
}
?>
</ul>

<ul id="cat_related">
<?php
global $post;
$cats = wp_get_post_categories($post->ID);
if ($cats) {
    $args = array(
		  'category__in' => array( $cats[0] ),
		  'post__not_in' => array( $post->ID ),
		  'showposts' => 6,
		  'caller_get_posts' => 1
	  );
  query_posts($args);

  if (have_posts()) {
    while (have_posts()) {
      the_post(); update_post_caches($posts); ?>
  <li>* <a href="<?php the_permalink(); ?>" rel="bookmark" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a></li>
<?php
    }
  } 
  else {
    echo '<li>* 暂无相关文章</li>';
  }
  wp_reset_query(); 
}
else {
  echo '<li>* 暂无相关文章</li>';
}
?>
</ul>

<ul id="tags_related">
<?php
global $post, $wpdb;
$post_tags = wp_get_post_tags($post->ID);
if ($post_tags) {
    $tag_list = '';
    foreach ($post_tags as $tag) {
        // 获取标签列表
        $tag_list .= $tag->term_id.',';
    }
    $tag_list = substr($tag_list, 0, strlen($tag_list)-1);

    $related_posts = $wpdb->get_results("
        SELECT DISTINCT ID, post_title
        FROM {$wpdb->prefix}posts, {$wpdb->prefix}term_relationships, {$wpdb->prefix}term_taxonomy
        WHERE {$wpdb->prefix}term_taxonomy.term_taxonomy_id = {$wpdb->prefix}term_relationships.term_taxonomy_id
        AND ID = object_id
        AND taxonomy = 'post_tag'
        AND post_status = 'publish'
        AND post_type = 'post'
        AND term_id IN (" . $tag_list . ")
        AND ID != '" . $post->ID . "'
        ORDER BY RAND()
        LIMIT 6");
        // 以上代码中的 6 为限制只获取6篇相关文章
        // 通过修改数字 6，可修改你想要的文章数量

    if ( $related_posts ) {
        foreach ($related_posts as $related_post) {
?>
    <li><a href="<?php echo get_permalink($related_post->ID); ?>" rel="bookmark" title="<?php echo $related_post->post_title; ?>"><?php echo $related_post->post_title; ?></a></li>
<?php   } 
    }
    else {
      echo '<li>暂无相关文章</li>';
    } 
}
else {
  echo '<li>暂无相关文章</li>';
}
?>
</ul>

<ul id="cat_related">
<?php
global $post, $wpdb;
$cats = wp_get_post_categories($post->ID);
if ($cats) {
  $related = $wpdb->get_results("
  SELECT post_title, ID
  FROM {$wpdb->prefix}posts, {$wpdb->prefix}term_relationships, {$wpdb->prefix}term_taxonomy
  WHERE {$wpdb->prefix}posts.ID = {$wpdb->prefix}term_relationships.object_id
  AND {$wpdb->prefix}term_taxonomy.taxonomy = 'category'
  AND {$wpdb->prefix}term_taxonomy.term_taxonomy_id = {$wpdb->prefix}term_relationships.term_taxonomy_id
  AND {$wpdb->prefix}posts.post_status = 'publish'
  AND {$wpdb->prefix}posts.post_type = 'post'
  AND {$wpdb->prefix}term_taxonomy.term_id = '" . $cats[0] . "'
  AND {$wpdb->prefix}posts.ID != '" . $post->ID . "'
  ORDER BY RAND( )
  LIMIT 6");

  if ( $related ) {
	  foreach ($related as $related_post) {
?>
	<li>* <a href="<?php echo get_permalink($related_post->ID); ?>" rel="bookmark" title="<?php echo $related_post->post_title; ?>"><?php echo $related_post->post_title; ?></a></li>
<?php
    } 
  }
  else {
    echo '<li>* 暂无相关文章</li>';
  } 
}
else {
  echo '<li>* 暂无相关文章</li>';
}
?>
</ul>

<ul id="author_related">
<?php
  global $post;
  $post_author = get_the_author_meta( 'user_login' );
  $args = array(
        'author_name' => $post_author,
        'post__not_in' => array($post->ID),
        'showposts' => 6,				// 显示相关文章数量
        'orderby' => date,			// 按时间排序
        'caller_get_posts' => 1
    );
  query_posts($args);

  if (have_posts()) {
    while (have_posts()) {
      the_post(); update_post_caches($posts); ?>
  <li>* <a href="<?php the_permalink(); ?>" rel="bookmark" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a></li>
<?php
    }
  }
  else { 
    echo '<li>* 暂无相关文章</li>';
  }
  wp_reset_query();
?>
</ul>