Skip to main content

reserve

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.

Reserves enough memory to accommodate a given number of elements

public function reserve(
  int $sz,
): void;

Reserves enough memory for $sz elements. If $sz is less than or equal to the current capacity of the current Vector, this method does nothing.

If $sz is less than zero, an exception is thrown.

Parameters​

  • int $sz - The pre-determined size you want for the current Vector.

Returns​

  • void

Examples​

This example reserves space for 1000 elements and then fills the Vector with 1000 integers:

const int VECTOR_SIZE = 1000;

<<__EntryPoint>>
function basic_usage_main(): void {
  $v = Vector {};
  $v->reserve(VECTOR_SIZE);

  for ($i = 0; $i < VECTOR_SIZE; $i++) {
    $v[] = $i * 10;
  }

  \var_dump($v);
}