get_adjacent_post( bool $in_same_term = false, int[]|string $excluded_terms = '', bool $previous = true, string $taxonomy = 'category' ): WP_Post|null|string
Retrieves the adjacent post.
Contents
Description
Can either be next or previous post.
Parameters
-
$in_same_term
bool Optional -
Whether post should be in the same taxonomy term.
Default:
false
-
$excluded_terms
int[]|string Optional -
Array or comma-separated list of excluded term IDs.
Default:
''
-
$previous
bool Optional -
Whether to retrieve previous post.
Default:
true
-
$taxonomy
string Optional -
Taxonomy, if
$in_same_term
is true. Default'category'
.Default:
'category'
Return
WP_Post|null|string Post object if successful. Null if global $post
is not set.
Empty string if no corresponding post exists.
Source
File: wp-includes/link-template.php
.
View all references
function get_adjacent_post( $in_same_term = false, $excluded_terms = '', $previous = true, $taxonomy = 'category' ) {
global $wpdb;
$post = get_post();
if ( ! $post || ! taxonomy_exists( $taxonomy ) ) {
return null;
}
$current_post_date = $post->post_date;
$join = '';
$where = '';
$adjacent = $previous ? 'previous' : 'next';
if ( ! empty( $excluded_terms ) && ! is_array( $excluded_terms ) ) {
// Back-compat, $excluded_terms used to be $excluded_categories with IDs separated by " and ".
if ( str_contains( $excluded_terms, ' and ' ) ) {
_deprecated_argument(
__FUNCTION__,
'3.3.0',
sprintf(
/* translators: %s: The word 'and'. */
__( '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', $excluded_terms );
}
/**
* Filters the IDs of terms excluded from adjacent post queries.
*
* The dynamic portion of the hook name, `$adjacent`, refers to the type
* of adjacency, 'next' or 'previous'.
*
* Possible hook names include:
*
* - `get_next_post_excluded_terms`
* - `get_previous_post_excluded_terms`
*
* @since 4.4.0
*
* @param int[]|string $excluded_terms Array of excluded term IDs. Empty string if none were provided.
*/
$excluded_terms = apply_filters( "get_{$adjacent}_post_excluded_terms", $excluded_terms );
if ( $in_same_term || ! empty( $excluded_terms ) ) {
if ( $in_same_term ) {
$join .= " INNER JOIN $wpdb->term_relationships AS tr ON p.ID = tr.object_id INNER JOIN $wpdb->term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id";
$where .= $wpdb->prepare( 'AND tt.taxonomy = %s', $taxonomy );
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( ',', array_map( 'intval', $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 ( $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'";
}
$op = $previous ? '<' : '>';
$order = $previous ? 'DESC' : 'ASC';
/**
* Filters the JOIN clause in the SQL for an adjacent post query.
*
* The dynamic portion of the hook name, `$adjacent`, refers to the type
* of adjacency, 'next' or 'previous'.
*
* Possible hook names include:
*
* - `get_next_post_join`
* - `get_previous_post_join`
*
* @since 2.5.0
* @since 4.4.0 Added the `$taxonomy` and `$post` parameters.
*
* @param string $join The JOIN clause in the SQL.
* @param bool $in_same_term Whether post should be in the same taxonomy term.
* @param int[]|string $excluded_terms Array of excluded term IDs. Empty string if none were provided.
* @param string $taxonomy Taxonomy. Used to identify the term used when `$in_same_term` is true.
* @param WP_Post $post WP_Post object.
*/
$join = apply_filters( "get_{$adjacent}_post_join", $join, $in_same_term, $excluded_terms, $taxonomy, $post );
/**
* Filters the WHERE clause in the SQL for an adjacent post query.
*
* The dynamic portion of the hook name, `$adjacent`, refers to the type
* of adjacency, 'next' or 'previous'.
*
* Possible hook names include:
*
* - `get_next_post_where`
* - `get_previous_post_where`
*
* @since 2.5.0
* @since 4.4.0 Added the `$taxonomy` and `$post` parameters.
*
* @param string $where The `WHERE` clause in the SQL.
* @param bool $in_same_term Whether post should be in the same taxonomy term.
* @param int[]|string $excluded_terms Array of excluded term IDs. Empty string if none were provided.
* @param string $taxonomy Taxonomy. Used to identify the term used when `$in_same_term` is true.
* @param WP_Post $post WP_Post object.
*/
$where = apply_filters( "get_{$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, $taxonomy, $post );
/**
* Filters the ORDER BY clause in the SQL for an adjacent post query.
*
* The dynamic portion of the hook name, `$adjacent`, refers to the type
* of adjacency, 'next' or 'previous'.
*
* Possible hook names include:
*
* - `get_next_post_sort`
* - `get_previous_post_sort`
*
* @since 2.5.0
* @since 4.4.0 Added the `$post` parameter.
* @since 4.9.0 Added the `$order` parameter.
*
* @param string $order_by The `ORDER BY` clause in the SQL.
* @param WP_Post $post WP_Post object.
* @param string $order Sort order. 'DESC' for previous post, 'ASC' for next.
*/
$sort = apply_filters( "get_{$adjacent}_post_sort", "ORDER BY p.post_date $order LIMIT 1", $post, $order );
$query = "SELECT p.ID FROM $wpdb->posts AS p $join $where $sort";
$key = md5( $query );
$last_changed = wp_cache_get_last_changed( 'posts' );
if ( $in_same_term || ! empty( $excluded_terms ) ) {
$last_changed .= wp_cache_get_last_changed( 'terms' );
}
$cache_key = "adjacent_post:$key:$last_changed";
$result = wp_cache_get( $cache_key, 'post-queries' );
if ( false !== $result ) {
if ( $result ) {
$result = get_post( $result );
}
return $result;
}
$result = $wpdb->get_var( $query );
if ( null === $result ) {
$result = '';
}
wp_cache_set( $cache_key, $result, 'post-queries' );
if ( $result ) {
$result = get_post( $result );
}
return $result;
}
Hooks
-
apply_filters( "get_{$adjacent}_post_excluded_terms",
int[]|string $excluded_terms ) -
Filters the IDs of terms excluded from adjacent post queries.
-
apply_filters( "get_{$adjacent}_post_join",
string $join ,bool $in_same_term ,int[]|string $excluded_terms ,string $taxonomy ,WP_Post $post ) -
Filters the JOIN clause in the SQL for an adjacent post query.
-
apply_filters( "get_{$adjacent}_post_sort",
string $order_by ,WP_Post $post ,string $order ) -
Filters the ORDER BY clause in the SQL for an adjacent post query.
-
apply_filters( "get_{$adjacent}_post_where",
string $where ,bool $in_same_term ,int[]|string $excluded_terms ,string $taxonomy ,WP_Post $post ) -
Filters the WHERE clause in the SQL for an adjacent post query.
Changelog
Version | Description |
---|---|
2.5.0 | Introduced. |
User Contributed Notes
You must log in before being able to contribute a note or feedback.
Examples
Link to previous post in the same taxonomy with Post Title for text.
Link to next post in the same taxonomy with Post Title for text.
I am not sure if there’s a function to get the next post of a post that maybe was retrieved from a custom loop or that isn’t the current
global $post;
. But sometimes, for design purposes, I have found the need to get the next post but in two levels. I searched for a function that works like this function but passing a custom $post as parameter.For example:
get_adjacent_post( $my_post, true, '', false, 'taxonomy_slug' );
. Where$my_post
is a custom post where I would like to get the next post of that specific post.I am not sure if currently exists that function, but could be great to have it accessible.