Format

:::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. :::

Given a valid format string (defined by SprintfFormatString), return a formatted string using $format_args

namespace HH\Lib\Str;

function format(
  SprintfFormatString $format_string,
  mixed ...$format_args,
): string;

Guides

• String
• Format Strings

Parameters

• SprintfFormatString $format_string
• mixed ...$format_args

Returns

• string