osFileManager is a rebranding of my Libra File Manager, the open source PHP file manager. After hundreds of thousands of downloads, this old code is still going strong.
Features include inline text file editing, uploading, secure download, user management, and permissions changes.
osFileManager comes in two flavors: static, which is a single file with only one user to mange files; and full, a database driven user database and permissions system for powerfull file management.