# The SplObjectStorage class

(PHP 5 >= 5.1.0, PHP 7)

## 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

SplObjectStorage implements Countable , Iterator , Serializable , ArrayAccess {
/* Methods */
public addAll ( SplObjectStorage `$storage` ) : void
public attach ( object `$object` [, mixed `$data` = `NULL` ] ) : void
public contains ( object `$object` ) : bool
public count ( ) : 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 `$object` [, mixed `$data` = `NULL` ] ) : void
public offsetUnset ( object `$object` ) : void
public removeAll ( SplObjectStorage `$storage` ) : void
public removeAllExcept ( SplObjectStorage `$storage` ) : void
public rewind ( ) : void
public serialize ( ) : string
public setInfo ( mixed `$data` ) : void
public unserialize ( string `$serialized` ) : 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)
    }

## Table of Contents

- SplObjectStorage::addAll — Adds all objects from another storage
- SplObjectStorage::attach — Adds an object in the storage
- SplObjectStorage::contains — Checks if the storage contains a specific object
- SplObjectStorage::count — Returns the number of objects in the storage
- SplObjectStorage::current — Returns the current storage entry
- SplObjectStorage::detach — Removes an object from the storage
- SplObjectStorage::getHash — Calculate a unique identifier for the contained objects
- SplObjectStorage::getInfo — Returns the data associated with the current iterator entry
- SplObjectStorage::key — Returns the index at which the iterator currently is
- SplObjectStorage::next — Move to the next entry
- SplObjectStorage::offsetExists — Checks whether an object exists in the storage
- SplObjectStorage::offsetGet — Returns the data associated with an object
- SplObjectStorage::offsetSet — Associates data to an object in the storage
- SplObjectStorage::offsetUnset — Removes an object from the storage
- SplObjectStorage::removeAll — Removes objects contained in another storage from the current storage
- SplObjectStorage::removeAllExcept — Removes all objects except for those contained in another storage from the current storage
- SplObjectStorage::rewind — Rewind the iterator to the first storage element
- SplObjectStorage::serialize — Serializes the storage
- SplObjectStorage::setInfo — Sets the data associated with the current iterator entry
- SplObjectStorage::unserialize — Unserializes a storage from its string representation
- SplObjectStorage::valid — Returns if the current iterator entry is valid