Aaron is concerned that a subtle difference between the Zend interpreter and HHVM's implementations of flock will prove problematic.
https://github.com/facebook/hhvm/blob/master/hphp/runtime/ext/ext_file.cpp#L353
Version: unspecified
Severity: normal
After a closer look at the man page and after to talking on HHVM a bit I think it should be fine:
"If a process uses open(2) (or similar) to obtain more than one descriptor for the same file, these descriptors are treated independently by flock(). An attempt to lock the file using one of these file descriptors may be denied by a lock that the calling process has already placed via another descriptor."