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wp_check_for_changed_slugs( int $post_id, WP_Post $post, WP_Post $post_before )

Check for changed slugs for published post objects and save the old slug.

Description

The function is used when a post object of any type is updated, by comparing the current and previous post objects.

If the slug was changed and not already part of the old slugs then it will be added to the post meta field (‘_wp_old_slug’) for storing old slugs for that post.

The most logically usage of this function is redirecting changed post objects, so that those that linked to an changed post will be redirected to the new post.

Parameters

$post_id

(int) (Required) Post ID.

$post

(WP_Post) (Required) The Post Object

$post_before

(WP_Post) (Required) The Previous Post Object

Source

File: wp-includes/post.php 

function wp_check_for_changed_slugs( $post_id, $post, $post_before ) {
	// Don't bother if it hasn't changed.
	if ( $post->post_name == $post_before->post_name ) {
		return;
	}

	// We're only concerned with published, non-hierarchical objects.
	if ( ! ( 'publish' === $post->post_status || ( 'attachment' === get_post_type( $post ) && 'inherit' === $post->post_status ) ) || is_post_type_hierarchical( $post->post_type ) ) {
		return;
	}

	$old_slugs = (array) get_post_meta( $post_id, '_wp_old_slug' );

	// If we haven't added this old slug before, add it now.
	if ( ! empty( $post_before->post_name ) && ! in_array( $post_before->post_name, $old_slugs, true ) ) {
		add_post_meta( $post_id, '_wp_old_slug', $post_before->post_name );
	}

	// If the new slug was used previously, delete it from the list.
	if ( in_array( $post->post_name, $old_slugs, true ) ) {
		delete_post_meta( $post_id, '_wp_old_slug', $post->post_name );
	}
}

Uses

Uses Description
wp-includes/post.php: get_post_meta()

Retrieves a post meta field for the given post ID.
wp-includes/post.php: add_post_meta()

Adds a meta field to the given post.
wp-includes/post.php: delete_post_meta()

Deletes a post meta field for the given post ID.
wp-includes/post.php: get_post_type()

Retrieves the post type of the current post or of a given post.
wp-includes/post.php: is_post_type_hierarchical()

Whether the post type is hierarchical.

Changelog

Version Description
2.1.0 Introduced.

© 2003–2019 WordPress Foundation
Licensed under the GNU GPLv2+ License.
https://developer.wordpress.org/reference/functions/wp_check_for_changed_slugs