WordPress函数get_previous_post()获取同分类下的上一篇文章

$in_same_term

(boolean) (可选) 是否属于同一分类

默认值: false

$excluded_categories

(string) (可选) 要排除的分类ID

默认值: ”

$taxonomy

(string) (可选) 分类法，如果$in_same_term为true。在WordPress3.8中添加。

默认值: ‘category’

示例：

<?php
$prev_post = get_previous_post();
if (!empty( $prev_post )): ?>
  <a href="<?php echo get_permalink( $prev_post->ID ); ?>"><?php echo $prev_post->post_title; ?></a>
<?php endif; ?>

源文件：

/**
 * Retrieve previous post that is adjacent to current post.
 *
 * @since 1.5.0
 *
 * @param bool         $in_same_term   Optional. Whether post should be in a same taxonomy term.
 * @param array|string $excluded_terms Optional. Array or comma-separated list of excluded term IDs.
 * @param string       $taxonomy       Optional. Taxonomy, if $in_same_term is true. Default 'category'.
 * @return null|string|WP_Post Post object if successful. Null if global $post is not set. Empty string if no corresponding post exists.
 */
function get_previous_post( $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' ) {
	return get_adjacent_post( $in_same_term, $excluded_terms, true, $taxonomy );
}