Smallest IDE for PHP with code-completion?

Geany is my editor of choice. It's small, cross-platform, (GTK) and supports literally dozens of languages. (including PHP) It has syntax highlighting, code-completion and even custom "build" commands. (such as php -l for sanity checks)

Netbeans is the best performing PHP editor with code completion that I have used; that said, it's by no means a lightweight editor. But I don't think any kind of editor with code completion is going to be truly lightweight.