I'd hazard a guess that should be:

  $user <> 0

Which, of course, would not display if someone had originally pasted this code straight into an HTML page without escaping it.

EDIT: Looks like it would show up. I wonder, then, if the <>s has been stripped. Some poorly written websites do that.

This is either a syntax error or a HipHop idiosyncrasy (was HHVM in use in 2007?)

$ php -r '$user = null; if ($user 0) { echo $user; }' PHP Parse error: syntax error, unexpected '0' (T_LNUMBER) in Command line code on line 1