Is Fun

:::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 is_fun(
  mixed $arg,
): bool;

Parameters

• mixed $arg

Returns

• bool