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 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)
}

Table of Contents

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User Contributed Notes 11 notes

up
65
Adam Monsen
10 years ago
Note some inconsistent/surprising behavior in SplObjectStorage to preserve backwards compatibility. You can't properly use foreach with key/value syntax.

<?php
$spl
= new SplObjectStorage ();
$keyForA = new StdClass();
$keyForB = new StdClass();
$spl[$keyForA] = 'value a';
$spl[$keyForB] = 'value b';
foreach (
$spl as $key => $value)
{
// $key is NOT an object, $value is!
// Must use standard array access to get strings.
echo $spl[$value] . "\n"; // prints "value a", then "value b"
}
// it may be clearer to use this form of foreach:
foreach ($spl as $key)
{
// $key is an object.
// Use standard array access to get values.
echo $spl[$key] . "\n"; // prints "value a", then "value b"
}
?>

See https://bugs.php.net/bug.php?id=49967
up
25
rafal at pawlukiewicz dot com
5 years ago
SplObjectStorage class can be nicely used in Observer pattern, for example:

<?php
class Subject implements \SplSubject
{
private
$observers;

public function
__construct()
{
$this->observers = new \SplObjectStorage;
}

public function
attach(\SplObserver $observer)
{
$this->observers->attach($observer);
}

public function
detach(\SplObserver $observer)
{
$this->observers->detach($observer);
}

public function
notify()
{
foreach (
$this->observers as $observer) {
$observer->update($this);
}
}
}
?>
up
12
frame86 at live dot com
8 years ago
Keep in mind that foreach() will copy your array before iterating, SplObjectStorage does not. If you have a sub call within an iteration that also calls foreach() on the object storage again, the iterator position collides!

To be safe use:
<?php
foreach(clone $myStorage as $obj) {

}
?>
up
10
m dot drewek at smf dot de
9 years ago
Please note that SplObjectStorage has a Bug introduced with 5.4.0, breaking object lookup in cloned instances of derived classes that overwrite getHash().

This is a confirmed Bug: https://bugs.php.net/bug.php?id=67582

Example:
<?php
class MyObjectStorage extends SplObjectStorage {
// Overwrite getHash() with just some (working) test-method
public function getHash($object) { return get_class($object); }
}

class
TestObject {}

$list = new MyObjectStorage(); // No issues if using "new SplObjectStorage()"
$list->attach(new TestObject());

foreach(
$list as $x) var_dump($list->offsetExists($x)); // TRUE

$list2 = clone $list;
foreach(
$list2 as $x) var_dump($list2->offsetExists($x)); // FALSE
?>
up
9
grzeniufication
7 years ago
<?php
/**
* For simple use cases (where you want to keep objects in a map)
* I would suggest to stick to an plain old array. Just use the object
* hash as array key.
*/
$entity1 = new stdClass();
$entity2 = new stdClass();
$entities = [];
$entities[spl_object_hash($entity1)] = $entity1;
$entities[spl_object_hash($entity2)] = $entity2;

// object hashes are hard to distinguish so you could run a hash function
// on them for better readability.
$entities[md5(spl_object_hash($entity1))] = $entity1;
$entities[md5(spl_object_hash($entity2))] = $entity2;

print_r($entities);
up
5
kris dot lamote at it-kitchen dot be
9 years ago
For anyone having issues with SplObjectStorages containing corrupt member variables after garbage collection (FatalErrorException after serializing): we used following fix to great effect
<?php

class FixedSplObjectStorage extends SplObjectStorage
{

public function
serialize()
{
$goodPortion = 'N;;m:a:0:{}';
$startKey = 'N;;m:a:';

$serialized = parent::serialize();

$startPos = strpos($serialized, $startKey);

if (
$startPos !== false) {
$serialized = substr_replace($serialized, $goodPortion, $startPos, -1);

}

return
$serialized;

}
}

?>
up
5
inwebo at gmail dot fr
12 years ago
I needed to merge SplObjectStorages.
<?php
// As an object set
$SplObjectStorage_1 = new SplObjectStorage();

$object1 = new StdClass;
$object1->attr = 'obj 1';
$object2 = new StdClass;
$object2->attr = 'obj 2';
$object3 = new StdClass;
$object3->attr = 'obj 3';

$SplObjectStorage_1->attach($object1);
$SplObjectStorage_1->attach($object2);
$SplObjectStorage_1->attach($object3);

// Another one object set
$SplObjectStorage_2 = new SplObjectStorage();

$object4 = new StdClass;
$object4->attr = 'obj 4';
$object5 = new StdClass;
$object5->attr = 'obj 5';
$object6 = new StdClass;
$object6->attr = 'obj 6';

$SplObjectStorage_2->attach($object4);
$SplObjectStorage_2->attach($object5);
$SplObjectStorage_2->attach($object6);

/**
* Merge SplObjectStorage
*
* @param how many SplObjectStorage params as you want
* @return SplObjectStorage
*/
function mergeSplObjectStorage() {

$buffer = new SplObjectStorage();

if(
func_num_args() > 0 ) {
$args = func_get_args();
foreach (
$args as $objectStorage) {
foreach(
$objectStorage as $object) {
if(
is_object( $object ) ) {
$buffer->attach($object);
}
}
}
}
else{
return
FALSE;
}
return
$buffer;
}

$merge = mergeSplObjectStorage($SplObjectStorage_1, $SplObjectStorage_2);

?>
<?php
echo $merge->count();
?>
Will output :
6

<?php
$merge
->rewind();
while(
$merge->valid()) {
$object = $merge->current();
var_dump($object);
$merge->next();
}
?>
Will ouput :
object(stdClass)#2 (1) {
["attr"]=>
string(5) "obj 1"
}
object(stdClass)#3 (1) {
["attr"]=>
string(5) "obj 2"
}
object(stdClass)#4 (1) {
["attr"]=>
string(5) "obj 3"
}
object(stdClass)#6 (1) {
["attr"]=>
string(5) "obj 4"
}
object(stdClass)#7 (1) {
["attr"]=>
string(5) "obj 5"
}
object(stdClass)#8 (1) {
["attr"]=>
string(5) "obj 6"
}

My two cents.
up
4
Marius
9 years ago
Do not use SplObjectStorage::detach when forach'ing over items in the storage as this skips the second (and only second) element.

Example:

<?php

class A {
public
$i;
public function
__construct($i) {
$this->i = $i;
}
}

$container = new \SplObjectStorage();

$container->attach(new A(1));
$container->attach(new A(2));
$container->attach(new A(3));
$container->attach(new A(4));
$container->attach(new A(5));

foreach (
$container as $item) {
echo
$item->i . "\n";
$container->detach($item);
}
echo
"== Left in storage ==\n";
foreach (
$container as $item) {
echo
$item->i . "\n";
}
/* Outputs:
1
3
4
5
== Left in storage ==
2
*/
?>
up
0
jan at odvarko dot cz
3 years ago
If you assign an array() to an object in SplObjectStorage and then try to modify its individual elements, you'll probably find it doesn't work.
Instead, you can use ArrayObject(), which will emulate array behaviour.

<?php

$storage
= new SplObjectStorage();

$obj1 = new StdClass();
$obj2 = new StdClass();

$storage[$obj1] = array();
$storage[$obj2] = new ArrayObject();

$storage[$obj1]['person'] = 'Jana'; // Won't work (PHP Notice: Indirect modification of overloaded element of SplObjectStorage has no effect)
$storage[$obj2]['person'] = 'Jana'; // Works

var_dump($storage[$obj1]['person']); // NULL (PHP Notice: Undefined index: person)
var_dump($storage[$obj2]['person']); // string(4) "Jana"

?>
up
0
divinity76 at gmail dot com
7 years ago
if you're looking for a ResourceStorage, check https://gist.github.com/divinity76/b8041e073b74bdeab562a075fc94217f

(i needed it for socket programming with socket_select())
up
0
Jan Walther
13 years ago
I rewrote some scripts and changed object storage with arrays to SplObjectStorage. At some point I needed support of array_rand() but I did not find a function to return a random attached object of an SplObjectStorage object.

So here is my solution for random access to SplObjectStorage:

<?php
$o1
= new StdClass;
$o2 = new StdClass;
$s = new SplObjectStorage;
$s->attach($o1);
$s->attach($o2);

$random = rand(0,$s->count()-1);
$s->rewind();
for(
$i=0;$i<$random;$i++) {
$s->next();
}
var_dump($s->current());
?>
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