The SplObjectStorage class

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

简介

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.

类摘要

SplObjectStorage implements Countable , Iterator , Serializable , ArrayAccess {
/* 方法 */
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|null
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
}

范例

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));
?>

以上例程会输出：

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]);
}
?>

以上例程会输出：

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

Table of Contents

User Contributed Notes

jan at odvarko dot cz 20-May-2021 06:32
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"

?>
rafal at pawlukiewicz dot com 04-Mar-2019 10:21
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);
        }
    }
}
?>
grzeniufication 15-Jul-2017 08:35
<?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);
divinity76 at gmail dot com 05-May-2017 05:58
if you're looking for a ResourceStorage, check https://gist.github.com/divinity76/b8041e073b74bdeab562a075fc94217f

(i needed it for socket programming with socket_select())
frame86 at live dot com 31-Aug-2016 08:29
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) {

}
?>
kris dot lamote at it-kitchen dot be 22-May-2015 07:41
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;

    }
}

?>
m dot drewek at smf dot de 28-Jan-2015 08:49
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
?>
Marius 20-Nov-2014 10:54
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
*/
?>
Adam Monsen 07-Jan-2014 05:48
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
inwebo at gmail dot fr 28-Feb-2012 11:01
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.
Jan Walther 30-Jun-2011 06:57
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());
?>
randallgirard at hotmail dot com 14-Dec-2009 12:01
I have two things to note about SplObjectStorage:

#1: A reference to the object itself is stored (not just a hash to compare against the object) and it must be removed before the object is destroyed and the destructor is executed.

#2: SplObjectStorage::rewind() MUST be called to initiate the iterator and before SplObjectStorage::current() will return an object (and I think the only way to retrieve an object?) rather than automatically starting at the first element as I expected it to, like an array for example. This assumption is based on SplObjectStorage::current() returning NULL until SplObjectStorage::rewind() is called once the objects are contained. As a note, always use REWIND before iterating through or fetching objects.

<?php

class foo {
    public function __destruct() {
        print("--- DESTRUCTOR FIRED!!<br />\r\n");
    }
}

# Create object and storage
$bar = new foo();
$s = new SplObjectStorage();

# Rewind early just as a test
$s->rewind();

# attach the object
$s->attach($bar, array('test'));

# Unset the object; destructor does NOT fire
unset($bar);
print("Object has been unset<br />\r\n");

# First demonstrate that REWIND must be called to initialize the iterator
$obj = $s->current();
var_dump($obj);
print("- Note the NULL (from \$s->current())<br />\r\n");

# Initialize, and then detach the current (and only) object
$s->rewind();
$s->detach( $s->current() );

# The destructor should NOW execute

?>

Output:

Object has been unset
NULL - Note the NULL (from $s->current())
--- DESTRUCTOR FIRED!!
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