KeyExists

:::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. :::

Check if a field in shape exists

public static function keyExists(
  shape() $shape,
  arraykey $index,
): bool;

Similar to array_key_exists, but for shapes.

Parameters

• shape() $shape
• arraykey $index

Returns

• bool

Examples

This example shows that keyExists returns true if a key exists in the Shape (even if the corresponding value is NULL):

function run(shape(?'x' => ?int, ?'y' => ?int, ?'z' => ?int) $point): void {
  // The key 'x' exists in Shape $point
  \var_dump(Shapes::keyExists($point, 'x'));

  // The key 'z' doesn't exist in $point
  \var_dump(Shapes::keyExists($point, 'z'));

  // The key 'y' exists in $point, even though its value is NULL
  \var_dump(Shapes::keyExists($point, 'y'));
}

<<__EntryPoint>>
function basic_usage_main(): void {
  run(shape('x' => 3, 'y' => null));
}