Source

File: wp-includes/post.php

function wp_trash_post( $post_id = 0 ) {
	if ( ! EMPTY_TRASH_DAYS ) {
		return wp_delete_post( $post_id, true );
	}

	$post = get_post( $post_id );

	if ( ! $post ) {
		return $post;
	}

	if ( 'trash' === $post->post_status ) {
		return false;
	}

	/**
	 * Filters whether a post trashing should take place.
	 *
	 * @since 4.9.0
	 *
	 * @param bool|null $trash Whether to go forward with trashing.
	 * @param WP_Post   $post  Post object.
	 */
	$check = apply_filters( 'pre_trash_post', null, $post );
	if ( null !== $check ) {
		return $check;
	}

	/**
	 * Fires before a post is sent to the Trash.
	 *
	 * @since 3.3.0
	 *
	 * @param int $post_id Post ID.
	 */
	do_action( 'wp_trash_post', $post_id );

	add_post_meta( $post_id, '_wp_trash_meta_status', $post->post_status );
	add_post_meta( $post_id, '_wp_trash_meta_time', time() );

	$post_updated = wp_update_post(
		array(
			'ID'          => $post_id,
			'post_status' => 'trash',
		)
	);

	if ( ! $post_updated ) {
		return false;
	}

	wp_trash_post_comments( $post_id );

	/**
	 * Fires after a post is sent to the Trash.
	 *
	 * @since 2.9.0
	 *
	 * @param int $post_id Post ID.
	 */
	do_action( 'trashed_post', $post_id );

	return $post;
}