This could not be more wrong. Meta is still using PHP AFAIK but I'm not sure it's modern. They created the Hack programming language ~10 years ago but it doesn't look like it's been updated in several years. Most of the improvements they touted were included in PHP 7 years ago.
HHVM was not a contribution to PHP. It resulted in PHP 7 being sped up and releasing with a bunch of long awaited features. But afaik , very little of HHVM made it back to PHP core.
This could not be more wrong. Meta is still using PHP AFAIK but I'm not sure it's modern. They created the Hack programming language ~10 years ago but it doesn't look like it's been updated in several years. Most of the improvements they touted were included in PHP 7 years ago.