HH\Set::firstKey

Returns the first "key" in the current Set.

Description

public function firstKey(): mixed

Returns the first "key" in the current Set.

Since Sets do not have keys, it returns the first value.

This method is interchangeable with firstValue().

Return Values

  • mixed - The first value in the current Set, or null if the Set is empty.

Examples

This example shows that firstKey returns the first value in the Set. An empty Set will return null as its first key.

<?hh

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

$s = Set {'red', 'green', 'blue', 'yellow'};
var_dump($s->firstKey());

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