Source

File: wp-includes/ms-site.php

function wp_delete_site( $site_id ) {
	global $wpdb;

	if ( empty( $site_id ) ) {
		return new WP_Error( 'site_empty_id', __( 'Site ID must not be empty.' ) );
	}

	$old_site = get_site( $site_id );
	if ( ! $old_site ) {
		return new WP_Error( 'site_not_exist', __( 'Site does not exist.' ) );
	}

	$errors = new WP_Error();

	/**
	 * Fires before a site should be deleted from the database.
	 *
	 * Plugins should amend the `$errors` object via its `WP_Error::add()` method. If any errors
	 * are present, the site will not be deleted.
	 *
	 * @since 5.1.0
	 *
	 * @param WP_Error $errors   Error object to add validation errors to.
	 * @param WP_Site  $old_site The site object to be deleted.
	 */
	do_action( 'wp_validate_site_deletion', $errors, $old_site );

	if ( ! empty( $errors->errors ) ) {
		return $errors;
	}

	/**
	 * Fires before a site is deleted.
	 *
	 * @since MU (3.0.0)
	 * @deprecated 5.1.0
	 *
	 * @param int  $site_id The site ID.
	 * @param bool $drop    True if site's table should be dropped. Default false.
	 */
	do_action_deprecated( 'delete_blog', array( $old_site->id, true ), '5.1.0' );

	/**
	 * Fires when a site's uninitialization routine should be executed.
	 *
	 * @since 5.1.0
	 *
	 * @param WP_Site $old_site Deleted site object.
	 */
	do_action( 'wp_uninitialize_site', $old_site );

	if ( is_site_meta_supported() ) {
		$blog_meta_ids = $wpdb->get_col( $wpdb->prepare( "SELECT meta_id FROM $wpdb->blogmeta WHERE blog_id = %d ", $old_site->id ) );
		foreach ( $blog_meta_ids as $mid ) {
			delete_metadata_by_mid( 'blog', $mid );
		}
	}

	if ( false === $wpdb->delete( $wpdb->blogs, array( 'blog_id' => $old_site->id ) ) ) {
		return new WP_Error( 'db_delete_error', __( 'Could not delete site from the database.' ), $wpdb->last_error );
	}

	clean_blog_cache( $old_site );

	/**
	 * Fires once a site has been deleted from the database.
	 *
	 * @since 5.1.0
	 *
	 * @param WP_Site $old_site Deleted site object.
	 */
	do_action( 'wp_delete_site', $old_site );

	/**
	 * Fires after the site is deleted from the network.
	 *
	 * @since 4.8.0
	 * @deprecated 5.1.0
	 *
	 * @param int  $site_id The site ID.
	 * @param bool $drop    True if site's tables should be dropped. Default false.
	 */
	do_action_deprecated( 'deleted_blog', array( $old_site->id, true ), '5.1.0' );

	return $old_site;
}