Count

:::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. :::

Returns the number of elements in the given Container

namespace HH\Lib\C;

function count(
  Container<mixed> $container,
): int;

Time complexity: O(1) Space complexity: O(1)

Parameters

• Container<mixed>$container

Returns

• int

Examples

$strings = vec["a", "b", "c", "d", "e"];
$count_result_1 = C\count($strings);
echo "First count result: $count_result_1\n";
//Output: First count result: 5

$empty_strings = vec[];
$count_result_2 = C\count($empty_strings);
echo "Second count result: $count_result_2\n";
//Output: Second count result: 0