facebook/hiphop-php — pull request #778 by nareshv (2013-05-17 04:24:20+00:00)
Title: add REQUEST_TIME_FLOAT to $_SERVER

Tested on my repo

[root@localhost ~]# hhvm server.php | grep REQUEST
[SELINUX_ROLE_REQUESTED] =>
[SELINUX_LEVEL_REQUESTED] =>
[REQUEST_START_TIME] => 1368169462
[REQUEST_TIME] => 1368169462
[REQUEST_TIME_FLOAT] => 1368169462.4599

EL6 rpm http://www.hop5.in/yum/el6/hiphop-php-2.1.210-1.el6.x86_64.rpm