I was wondering if anyone has found a way to detect whether a PHP script/program is run through Facebook's HipHop or the "regular" environment (CLI, mod_php, CGI).
Currently the workaround I am using is looking for an unimplemented feature (for instance PHP 5.3 functions) and checking for the availability of said feature. Of course, this is rather a dodgy hack (and not portable) since as HipHop matures, more and more features will be implemented.
$_ENV['HPHP']
is set to 1 when running under HipHop.
Thanks to nicolasff for the solution
Ref: https://github.com/facebook/hiphop-php/issues/382#issuecomment-1754648