ImmVector

:::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. :::

ImmVector is an immutable Vector

HHVM provides a native implementation for this class. The PHP class definition below is not actually used at run time; it is simply provided for the typechecker and for developer reference.

An ImmVector cannot be mutated. No elements can be added to it or removed from it, nor can elements be overwritten using assignment (i.e. $c[$k] = $v is not allowed).

$v = Vector {1, 2, 3};
$fv = $v->toImmVector();

construct it with a Traversable:

$a = vec[1, 2, 3];
$fv = new ImmVector($a);

or use the literal syntax:

$fv = ImmVector {1, 2, 3};

Guides

• Introduction
• Classes

Interface Synopsis

namespace HH;

final class ImmVector implements \ConstVector<Tv> {...}

Public Methods

• ::fromItems(?Traversable<Tv> $iterable): ImmVector<Tv>
  Creates an ImmVector from the given Traversable, or an empty ImmVector if null is passed
• ::fromKeysOf<Tk as arraykey>(?KeyedContainer<Tk, mixed> $container): ImmVector<Tk>
  Creates an ImmVector from the keys of the specified container
• ->__construct(?Traversable<Tv> $iterable = NULL): void
  Creates an ImmVector from the given Traversable, or an empty ImmVector if null is passed
• ->__toString(): string
  Returns the string version of the current ImmVector, which is "ImmVector"
• ->at(int $key): Tv
  Returns the value at the specified key in the current ImmVector
• ->concat<Tu super Tv>(Traversable<Tu> $traversable): ImmVector<Tu>
  Returns an ImmVector that is the concatenation of the values of the current ImmVector and the values of the provided Traversable
• ->containsKey(mixed $key): bool
  Determines if the specified key is in the current ImmVector
• ->count(): int
  Returns the number of elements in the current ImmVector
• ->filter((function(Tv): bool) $callback): ImmVector<Tv>
  Returns a ImmVector containing the values of the current ImmVector that meet a supplied condition
• ->filterWithKey((function(int, Tv): bool) $callback): ImmVector<Tv>
  Returns an ImmVector containing the values of the current ImmVector that meet a supplied condition applied to its keys and values
• ->firstKey(): ?int
  Returns the first key in the current ImmVector
• ->firstValue(): ?Tv
  Returns the first value in the current ImmVector
• ->get(int $key): ?Tv
  Returns the value at the specified key in the current ImmVector
• ->getIterator(): KeyedIterator<int, Tv>
  Returns an iterator that points to beginning of the current ImmVector
• ->immutable(): ImmVector<Tv>
  Returns the current ImmVector
• ->isEmpty(): bool
  Checks if the current ImmVector is empty
• ->items(): Iterable<Tv>
  Returns an Iterable view of the current ImmVector
• ->keys(): ImmVector<int>
  Returns an ImmVector containing the keys, as values, of the current ImmVector
• ->lastKey(): ?int
  Returns the last key in the current ImmVector
• ->lastValue(): ?Tv
  Returns the last value in the current ImmVector
• ->lazy(): KeyedIterable<int, Tv>
  Returns a lazy, access-elements-only-when-needed view of the current ImmVector
• ->linearSearch(mixed $search_value): int
  Returns the index of the first element that matches the search value
• ->map<Tu>((function(Tv): Tu) $callback): ImmVector<Tu>
  Returns an ImmVector containing the results of applying an operation to each value in the current ImmVector
• ->mapWithKey<Tu>((function(int, Tv): Tu) $callback): ImmVector<Tu>
  Returns an ImmVector containing the results of applying an operation to each key/value pair in the current ImmVector
• ->skip(int $n): ImmVector<Tv>
  Returns an ImmVector containing the values after the $n-th element of the current ImmVector
• ->skipWhile((function(Tv): bool) $fn): ImmVector<Tv>
  Returns an ImmVector containing the values of the current ImmVector starting after and including the first value that produces false when passed to the specified callback
• ->slice(int $start, int $len): ImmVector<Tv>
  Returns a subset of the current ImmVector starting from a given key up to, but not including, the element at the provided length from the starting key
• ->take(int $n): ImmVector<Tv>
  Returns an ImmVector containing the first $n values of the current ImmVector
• ->takeWhile((function(Tv): bool) $callback): ImmVector<Tv>
  Returns an ImmVector containing the values of the current ImmVector up to but not including the first value that produces false when passed to the specified callback
• ->toDArray(): darray<int, Tv>
• ->toImmMap(): ImmMap<int, Tv>
  Returns an immutable integer-keyed Map (ImmMap) based on the elements of the current ImmVector
• ->toImmSet(): ImmSet<Tv>
  Returns an immutable Set (ImmSet) with the values of the current ImmVector
• ->toImmVector(): ImmVector<Tv>
  Returns the current ImmVector
• ->toKeysArray(): varray<Tv>
  Returns an array whose values are the keys from the current ImmVector
• ->toMap(): Map
  Returns a Map built from the keys and values of this ImmVector
• ->toSet(): Set
  Returns a Set built from the values of this ImmVector
• ->toVArray(): varray<Tv>
  Returns a varray built from the values from this ImmVector
• ->toValuesArray(): varray<Tv>
  Returns an array containing the values from the current ImmVector
• ->toVector(): Vector
  Returns a Vector built from the values of this ImmVector
• ->values(): ImmVector<Tv>
  Returns a new ImmVector containing the values of the current ImmVector; that is, a copy of the current ImmVector
• ->zip<Tu>(Traversable<Tu> $traversable): ImmVector<Pair<Tv, Tu>>
  Returns an ImmVector where each element is a Pair that combines the element of the current ImmVector and the provided Traversable