bp_document_create_folder_recursive( $array, bool $parent_folder )

function bp_document_create_folder_recursive( $array, $parent_folder ) {

	// Base case: an empty array produces no list.
	if ( empty( $array ) || empty( $parent_folder ) ) {
		return '';
	}

	foreach ( $array as $item ) {

		$id    = $item['id'];
		$title = $item['title'];
		$child = $item['children'];

		// Create given main parent folder.
		$sub_parent_folder = $parent_folder . '/' . $title;
		wp_mkdir_p( $sub_parent_folder );

		// Fetch all the attachments of the parent folder.
		$get_current_attachments = bp_document_get_folder_attachment_ids( $id );
		if ( ! empty( $get_current_attachments ) ) {
			foreach ( $get_current_attachments as $attachment ) {
				$the_file  = get_attached_file( $attachment->attachment_id );
				$file_name = basename( $the_file );
				copy( $the_file, $sub_parent_folder . '/' . $file_name );
			}
		}
		if ( ! empty( $child ) ) {
			bp_document_create_folder_recursive( $child, $sub_parent_folder );
		}
	}
}