获取相邻文章
描述
检索相邻的文章，可以是上一篇或下一篇。
function wphun_insert_query_vars( $vars )
{
//新增参数
array_push($vars, ‘function_name’);
return $vars;
}用法
<?php get_adjacent_post( $in_same_term, $excluded_terms, $previous, $taxonomy ) ?>参数
$in_same_term
(boolean) （可选）文章是否在同一分类。
默认值: false
$excluded_terms
(array or string) (可选) 排除分类的ID。
默认值: ”
$previous
(boolean) （可选）是否检索之前的文章。
默认值: true
$taxonomy
(string) (可选) 限定的分类名称，如果 $in_same_term 设置为 true。
默认值: ‘category’
返回值
如果成功，返回文章对象。
如果 global $post 没有设置，返回空值Null。
如果不存在符合条件的文章，返回空字符串。
示例
获取同分类下的上一篇文章。
<?php $prev_post = get_adjacent_post( true, ”, true, ‘taxonomy_slug’ ); ?>
<?php if ( is_a( $prev_post, ‘WP_Post’ ) ) { ?>
<a href=“<?php echo get_permalink( $prev_post->ID ); ?>“><?php echo get_the_title( $prev_post->ID ); ?></a>
<?php } ?>获取同分类下的下一篇文章。
<?php $next_post = get_adjacent_post( true, ”, false, ‘taxonomy_slug’ ); ?>
<?php if ( is_a( $next_post, ‘WP_Post’ ) ) { ?>
<a href=“<?php echo get_permalink( $next_post->ID ); ?>“><?php echo get_the_title( $next_post->ID ); ?></a>
<?php } ?>注意
使用 global: (object) $post
使用 global: (object) $wpdb
Filters过滤器
$adjacent 是 ‘previous’（上一篇） or ‘next’（下一篇）。
“get_{$adjacent}_post_join”:
$join, $in_same_cat, $excluded_categories
“get_{$adjacent}_post_where”:
$wpdb->prepare(“WHERE p.post_date $op %s AND p.post_type = %s AND p.post_status = ‘publish’ $posts_in_ex_cats_sql”, $current_post_date, $post->post_type), $in_same_cat, $excluded_categories
“get_{$adjacent}_post_sort”:
“ORDER BY p.post_date $order LIMIT 1”
历史
添加于 版本: 2.5.0
源文件
get_adjacent_post() 函数的代码位于 wp-includes/link-template.php.
/**
* Retrieve adjacent post.
*
* Can either be next or previous post.
*
* @since 2.5.0
*
* @global wpdb $wpdb
*
* @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 bool $previous Optional. Whether to retrieve previous post.
* @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_adjacent_post( $in_same_term = false, $excluded_terms = ”, $previous = true, $taxonomy = ‘category’ ) {
global $wpdb;
if ( ( ! $post = get_post() ) || ! taxonomy_exists( $taxonomy ) )
return null;
$current_post_date = $post->post_date;
$join = ”;
$where = ”;
if ( $in_same_term || ! empty( $excluded_terms ) ) {
$join = ” INNER JOIN $wpdb->term_relationships AS tr ON p.ID = tr.object_id INNER JOIN $wpdb->term_taxonomy tt ON tr.term_taxonomy_id = tt.term_taxonomy_id”;
$where = $wpdb->prepare( “AND tt.taxonomy = %s”, $taxonomy );
if ( ! empty( $excluded_terms ) && ! is_array( $excluded_terms ) ) {
// back-compat, $excluded_terms used to be $excluded_terms with IDs separated by ” and “
if ( false !== strpos( $excluded_terms, ‘ and ‘ ) ) {
_deprecated_argument( __FUNCTION__, ‘3.3’, sprintf( __( ‘Use commas instead of %s to separate excluded terms.’ ), “‘and’” ) );
$excluded_terms = explode( ‘ and ‘, $excluded_terms );
} else {
$excluded_terms = explode( ‘,’, $excluded_terms );
}
$excluded_terms = array_map( ‘intval’, $excluded_terms );
}
if ( $in_same_term ) {
if ( ! is_object_in_taxonomy( $post->post_type, $taxonomy ) )
return ”;
$term_array = wp_get_object_terms( $post->ID, $taxonomy, array( ‘fields’ => ‘ids’ ) );
// Remove any exclusions from the term array to include.
$term_array = array_diff( $term_array, (array) $excluded_terms );
$term_array = array_map( ‘intval’, $term_array );
if ( ! $term_array || is_wp_error( $term_array ) )
return ”;
$where .= ” AND tt.term_id IN (“ . implode( ‘,’, $term_array ) . “)”;
}
if ( ! empty( $excluded_terms ) ) {
$where .= ” AND p.ID NOT IN ( SELECT tr.object_id FROM $wpdb->term_relationships tr LEFT JOIN $wpdb->term_taxonomy tt ON (tr.term_taxonomy_id = tt.term_taxonomy_id) WHERE tt.term_id IN (“ . implode( $excluded_terms, ‘,’ ) . ‘) )’;
}
}
// ‘post_status’ clause depends on the current user.
if ( is_user_logged_in() ) {
$user_id = get_current_user_id();
$post_type_object = get_post_type_object( $post->post_type );
if ( empty( $post_type_object ) ) {
$post_type_cap = $post->post_type;
$read_private_cap = ‘read_private_’ . $post_type_cap . ‘s’;
} else {
$read_private_cap = $post_type_object->cap->read_private_posts;
}
/*
* Results should include private posts belonging to the current user, or private posts where the
* current user has the ‘read_private_posts’ cap.
*/
$private_states = get_post_stati( array( ‘private’ => true ) );
$where .= ” AND ( p.post_status = ‘publish’”;
foreach ( (array) $private_states as $state ) {
if ( current_user_can( $read_private_cap ) ) {
$where .= $wpdb->prepare( ” OR p.post_status = %s”, $state );
} else {
$where .= $wpdb->prepare( ” OR (p.post_author = %d AND p.post_status = %s)”, $user_id, $state );
}
}
$where .= ” )”;
} else {
$where .= ” AND p.post_status = ‘publish’”;
}
$adjacent = $previous ? ‘previous’ : ‘next’;
$op = $previous ? ‘<‘ :=“” ‘=””>’;
$order = $previous ? ‘DESC’ : ‘ASC’;
/**
* Filter the JOIN clause in the SQL for an adjacent post query.
*
* The dynamic portion of the hook name, `$adjacent`, refers to the type
* of adjacency, ‘next’ or ‘previous’.
*
* @since 2.5.0
*
* @param string $join The JOIN clause in the SQL.
* @param bool $in_same_term Whether post should be in a same taxonomy term.
* @param array $excluded_terms Array of excluded term IDs.
*/
$join = apply_filters( “get_{$adjacent}_post_join”, $join, $in_same_term, $excluded_terms );
/**
* Filter the WHERE clause in the SQL for an adjacent post query.
*
* The dynamic portion of the hook name, `$adjacent`, refers to the type
* of adjacency, ‘next’ or ‘previous’.
*
* @since 2.5.0
*
* @param string $where The `WHERE` clause in the SQL.
* @param bool $in_same_term Whether post should be in a same taxonomy term.
* @param array $excluded_terms Array of excluded term IDs.
*/
$where = apply_filters( “get_{$adjacent}_post_where”, $wpdb->prepare( “WHERE p.post_date $op %s AND p.post_type = %s $where”, $current_post_date, $post->post_type ), $in_same_term, $excluded_terms );
/**
* Filter the ORDER BY clause in the SQL for an adjacent post query.
*
* The dynamic portion of the hook name, `$adjacent`, refers to the type
* of adjacency, ‘next’ or ‘previous’.
*
* @since 2.5.0
*
* @param string $order_by The `ORDER BY` clause in the SQL.
*/
$sort = apply_filters( “get_{$adjacent}_post_sort”, “ORDER BY p.post_date $order LIMIT 1” );
$query = “SELECT p.ID FROM $wpdb->posts AS p $join $where $sort”;
$query_key = ‘adjacent_post_’ . md5( $query );
$result = wp_cache_get( $query_key, ‘counts’ );
if ( false !== $result ) {
if ( $result )
$result = get_post( $result );
return $result;
}
$result = $wpdb->get_var( $query );
if ( null === $result )
$result = ”;
wp_cache_set( $query_key, $result, ‘counts’ );
if ( $result )
$result = get_post( $result );
return $result;
}
</‘>相关
get_next_post(), get_previous_post()
原文：http://codex.wordpress.org/Function_Reference/get_adjacent_post
