HH\Lib\C\find_key

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

Returns the key of the first value of the given KeyedTraversable for which the predicate returns true, or null if no such value is found

namespace HH\Lib\C;

function find_key<Tk, Tv>(
  KeyedTraversable<Tk, Tv> $traversable,
  (function(Tv):bool) $value_predicate,
): ?Tk;

Parameters