WP_Importer::set_blog( int $blog_id )

	public function set_blog( $blog_id ) {
		if ( is_numeric( $blog_id ) ) {
			$blog_id = (int) $blog_id;
		} else {
			$blog = 'http://' . preg_replace( '#^https?://#', '', $blog_id );
			if ( ( !$parsed = parse_url( $blog ) ) || empty( $parsed['host'] ) ) {
				fwrite( STDERR, "Error: can not determine blog_id from $blog_id\n" );
				exit();
			}
			if ( empty( $parsed['path'] ) ) {
				$parsed['path'] = '/';
			}
			$blogs = get_sites( array( 'domain' => $parsed['host'], 'number' => 1, 'path' => $parsed['path'] ) );
			if ( ! $blogs ) {
				fwrite( STDERR, "Error: Could not find blog\n" );
				exit();
			}
			$blog = array_shift( $blogs );
			$blog_id = (int) $blog->blog_id;
		}

		if ( function_exists( 'is_multisite' ) ) {
			if ( is_multisite() )
				switch_to_blog( $blog_id );
		}

		return $blog_id;
	}