In Sublime Text I can arbitrarily select a set of lines and then use ⌘+L to expand the selection to the full lines. Is there a similar command in PHPStorm / Web
With WebStorm 11 (at least) the multi-caret keyboard shortcut is:
Ctrl then Ctrl+Arrow Up (or click & drag with the middle mouse button/scroll wheel)
then to select the full lines:
Home then Shift+End
which you could even create as a macro with a keyboard shortcut.
I used to accidentally activate the multi-caret all the time (I scroll with Ctrl+Up/Down), so I knew how to do part of it, but it took me ages to figure out that extra Ctrl tap at the beginning.