I generally (note: not always as there are exceptions!) follow the idea of adding a space between language construct and opening parenthesis, and no space between function name and opening parenthesis. That's always true for functions, but I commonly neglect the space for isset/unset/empty and probably some others that my mind doesn't want to conjure up at this moment.

Back to the original poll question, I always add a space after if, else, while and for. (Note: if you ever see code from me without that space, don't shoot me. It's likely just a typing mistake.)