ContainsKey

:::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. :::

Determines if the specified key is in the current Vector

public function containsKey(
  mixed $key,
): bool;

Guide

• Constraints

Parameters

• mixed $key

Returns

• bool - true if the specified key is present in the current Vector; returns false otherwise.

Examples

$v = Vector {'red', 'green', 'blue', 'yellow'};

// Prints "true", since index 0 is the first element
\var_dump($v->containsKey(0));

// Prints "true", since index 3 is the last element
\var_dump($v->containsKey(3));

// Prints "false", since index 10 doesn't exist
\var_dump($v->containsKey(10));