This API is part of the Hack Standard Library, not HHVM itself.
Facebook Engineer?

This function is available as C\any() in Facebook's www repository.

Returns true if the given predicate returns true for any element of the given Traversable


namespace HH\Lib\C;

function any<T>(
  Traversable<T> $traversable,
  ?(function(T):bool) $predicate = null,
): bool;

If no predicate is provided, it defaults to casting the element to bool.

If you're looking for C\none, use !C\any.