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)
}

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

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User Contributed Notes 11 notes

down

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

down

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);
        }
    }
}
?>

down

frame86 at live dot com ¶

7 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) {

}
?>

down

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
?>

down

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);

down

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;

    }
}

?>

down

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.

down

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
*/
?>

down

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"

?>

down

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())

down

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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The SplObjectStorage class

Introduction

Class synopsis

Examples

Table of Contents

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User Contributed Notes 11 notes