Source

File: wp-includes/post.php

function wp_transition_post_status( $new_status, $old_status, $post ) {
	/**
	 * Fires when a post is transitioned from one status to another.
	 *
	 * @since 2.3.0
	 *
	 * @param string  $new_status New post status.
	 * @param string  $old_status Old post status.
	 * @param WP_Post $post       Post object.
	 */
	do_action( 'transition_post_status', $new_status, $old_status, $post );

	/**
	 * Fires when a post is transitioned from one status to another.
	 *
	 * The dynamic portions of the hook name, `$new_status` and `$old status`,
	 * refer to the old and new post statuses, respectively.
	 *
	 * @since 2.3.0
	 *
	 * @param WP_Post $post Post object.
	 */
	do_action( "{$old_status}_to_{$new_status}", $post );

	/**
	 * Fires when a post is transitioned from one status to another.
	 *
	 * The dynamic portions of the hook name, `$new_status` and `$post->post_type`,
	 * refer to the new post status and post type, respectively.
	 *
	 * Please note: When this action is hooked using a particular post status (like
	 * 'publish', as `publish_{$post->post_type}`), it will fire both when a post is
	 * first transitioned to that status from something else, as well as upon
	 * subsequent post updates (old and new status are both the same).
	 *
	 * Therefore, if you are looking to only fire a callback when a post is first
	 * transitioned to a status, use the {@see 'transition_post_status'} hook instead.
	 *
	 * @since 2.3.0
	 *
	 * @param int     $post_id Post ID.
	 * @param WP_Post $post    Post object.
	 */
	do_action( "{$new_status}_{$post->post_type}", $post->ID, $post );
}