get_adjacent_post( bool $in_same_term = false, array|string $excluded_terms = ”, bool $previous = true, string $taxonomy = ‘category’ )
Retrieves the adjacent post.
Description
Can either be next or previous post.
Parameters
- $in_same_term
-
(bool) (Optional) Whether post should be in a same taxonomy term.
Default value: false
- $excluded_terms
-
(array|string) (Optional) Array or comma-separated list of excluded term IDs.
Default value: ”
- $previous
-
(bool) (Optional) Whether to retrieve previous post. Default true
Default value: true
- $taxonomy
-
(string) (Optional) Taxonomy, if $in_same_term is true.
Default value: ‘category’
Return
(null|string|WP_Post) 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
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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 ( false !== strpos ( $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'. * * @since 4.4.0 * * @param array $excluded_terms Array of excluded term IDs. */ $excluded_terms = apply_filters( "get_{$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 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 ( ( 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'" ; } $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'. * * @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 a same taxonomy term. * @param array $excluded_terms Array of excluded term IDs. * @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'. * * @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 a same taxonomy term. * @param array $excluded_terms Array of excluded term IDs. * @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'. * * @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" ; $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 ; } |
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Changelog
Version | Description |
---|---|
2.5.0 | Introduced. |