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vmk

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.

Returns an Awaitable of Vector after a mapping operation has been applied to each key and value in the provided KeyedTraversable

namespace HH\Asio;

function vmk<Tk, Tv, Tr>(
  KeyedTraversable<Tk, Tv> $inputs,
  (function(Tk, Tv): Awaitable<Tr>) $callable,
): Awaitable<Vector<Tr>>;

This function is similar to vm(), but passes element keys to the callable as well.

This function is similar to Vector::mapWithKey(), but the mapping of the keys and values is done using Awaitables.

This function is called vmk because we are returning a vector and doing a mapping operation that includes keys.

$callable must return an Awaitable.

The values in the Vector of the returned Awaitable are not available until you await or join the returned Awaitable.

Parameters​

Returns​

Examples​

/**
 * Query an arbitrary number of URLs in parallel
 * returning them as a Vector of string responses.
 */
async function get_urls(\ConstVector<string> $urls): Awaitable<Vector<string>> {

  // Await on curl requests in parallel and
  // prepend the request ID index
  return await \HH\Asio\vmk(
    $urls,
    async ($idx, $url) ==> {
      $content = await \HH\Asio\curl_exec($url);
      return $idx." => ".$content;
    },
  );
}

<<__EntryPoint>>
async function basic_usage_main(): Awaitable<void> {
  $urls = ImmVector {
    "http://example.com",
    "http://example.net",
    "http://example.org",
  };

  $pages = await get_urls($urls);
  foreach ($pages as $page) {
    echo \substr($page, 0, 20).' ... '.\substr($page, -8);
  }
}
```.skipif
// Skip if we don't have an internet connection
if (!\get_headers("www.example.com")) {
  print "skip";
}