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, SeekableIterator, 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 seek(int $offset): 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)
}

    Changelog

    Version Description
    8.4.0 Implement SeekableIterator, previously only Iterator was implemented.

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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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