I recently updated my Eclipse (now running 20100218-1602), and I've found whenever I click around quickly between tabs on the tab bar, it will sometimes maximize the editor and hide the PHP Explorer to the left. After researching a little, this appears to be a feature of double clicking a tab. So I guess it's my fault, I'm sure I'm clicking around too fast and mistakenly double clicking a tab, but it happens often enough on what I'd consider a normal editing session that I've come to absolutely loathe it, and even after the usual googling due diligence cannot figure out how to turn it off.
From this post (http://stackoverflow.com/questions/594659/eclipses-tab-double-click-on-visual-studio) someone mentions the Window.AutoHideAll shortcut, however that seems to only be for assigning keyboard shortcuts--this is a mouse click thing. But maybe it's a clue.
I can't find anything relevant under Eclipse - Preferences - PHP. I don't think it's specific to PHP because if I switch to the Java perspective, double clicking a tab hides the Package Explorer.
Any suggestions are appreciated, thanks!