Idx Readonly

:::info[Note] This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information. :::

namespace HH;

function idx_readonly<Tk as arraykey, Tv>(
  ?KeyedContainer<Tk, Tv> $collection,
  ?Tk $index,
  $default = NULL,
): Tv;

Parameters

• ?KeyedContainer<Tk,Tv> $collection
• ?Tk $index
• $default = NULL

Returns

• Tv