Note: Most WSN Knowledge Base users don't need to edit PHP, and thus don't need a PHP editor.

Although you can edit PHP in a plain text editor, it can be quite useful to have line numbering, syntax highlighting, integrated function reference, function lists, and other such features you won't find in your standard text editor.

Eclipse is a cross-platform development tool with a PHP plugin.

For Linux, gPHPEdit is an excellent PHP editor: http://www.gphpedit.org
It's used for WSN development. Quanta Plus is also an option.

For Windows and Mac, see http://www.php-editors.com/ for your options.