HH\Map::firstKey

Returns the first key in the current Map

Description

public function firstKey(): ?Tk

Return Values

  • ?Tk - The first key in the current Map, or null if the Map is empty.

Examples

The following example gets the first key from Map. An empty Map will return null as its first key.

<?hh

namespace Hack\UserDocumentation\API\Examples\Map\FirstKey;

$m = Map {
  'red' => '#ff0000',
  'green' => '#00ff00',
  'blue' => '#0000ff',
  'yellow' => '#ffff00',
};
var_dump($m->firstKey());

$m = Map {};
var_dump($m->firstKey());
Output
string(3) "red"
NULL