Phpseclib

phpseclib is a 3rd-party library which implements SFTP (and SSH2) entirely in native PHP code. It exists in large part because of PHP's native support for SFTP being somewhat undependable and incomplete.

• official site
  • SFTP guide
• code docs:
  • 3.0 (what I'm using as of 2026-07-23; 4.0 is apparently in progress but not documented yet)
    • SSH2
    • SFTP
    • Stream

Its SFTP class descends from its SSH2 class, so you can use a single SFTP object to handle both (...as I understand it on 2026-07-22; I'm going to be testing that theory soon).