The SplObjectStorage class

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

Introduction

The SplObjectStorage class provides a map from objects to data or, by ignoring data, an object set. This dual purpose can be useful in many cases involving the need to uniquely identify objects.

Class synopsis

class SplObjectStorage implements Countable, Iterator, Serializable, ArrayAccess {
/* Methods */
public addAll(SplObjectStorage $storage): int
public attach(object $object, mixed $info = null): void
public contains(object $object): bool
public count(int $mode = COUNT_NORMAL): int
public current(): object
public detach(object $object): void
public getHash(object $object): string
public getInfo(): mixed
public key(): int
public next(): void
public offsetExists(object $object): bool
public offsetGet(object $object): mixed
public offsetSet(object $object, mixed $info = null): void
public offsetUnset(object $object): void
public removeAll(SplObjectStorage $storage): int
public removeAllExcept(SplObjectStorage $storage): int
public rewind(): void
public serialize(): string
public setInfo(mixed $info): void
public unserialize(string $data): void
public valid(): bool
}

Examples

Example #1 SplObjectStorage as a set

<?php
// As an object set
$s = new SplObjectStorage();

$o1 = new StdClass;
$o2 = new StdClass;
$o3 = new StdClass;

$s->attach($o1);
$s->attach($o2);

var_dump($s->contains($o1));
var_dump($s->contains($o2));
var_dump($s->contains($o3));

$s->detach($o2);

var_dump($s->contains($o1));
var_dump($s->contains($o2));
var_dump($s->contains($o3));
?>

The above example will output:

bool(true)
bool(true)
bool(false)
bool(true)
bool(false)
bool(false)

Example #2 SplObjectStorage as a map

<?php
// As a map from objects to data
$s = new SplObjectStorage();

$o1 = new StdClass;
$o2 = new StdClass;
$o3 = new StdClass;

$s[$o1] = "data for object 1";
$s[$o2] = array(1,2,3);

if (isset($s[$o2])) {
    var_dump($s[$o2]);
}
?>

The above example will output:

array(3) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
}

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