unserialize

(PHP 4, PHP 5, PHP 7, PHP 8)

unserialize — Erzeugt aus einem gespeicherten Datenformat einen Wert in PHP

Beschreibung

unserialize(string $data, array $options = []): mixed

unserialize() nimmt eine einzelne Variable aus einer serialisierten Datenmenge und wandelt sie in einen PHP-Wert zurück.

Warnung

Unvertrauenswürdige Benutzereingaben sollten nicht an unserialize() übergeben werden, unabhängig vom options-Wert von allowed_classes. Die Deserialisierung kann durch Objektinstanziierung und Autoloading dazu führen, dass Code geladen und ausgeführt wird, und ein böswilliger Anwender kann in der Lage sein, das auszunutzen. Es ist ein sicheres, standardisiertes Austauschformat wie JSON (per json_decode() und json_encode()) zu verwenden, wenn serialisierte Daten an den Nutzer übergeben werden müssen.

Müssen extern gespeicherte serialisierte Daten deserialisiert werden, ist zu erwägen hash_hmac() zur Datenvalidierung zu verwenden. Es ist sicherzustellen, dass die Daten von niemandem außer einem selbst modifiziert wurden.

Parameter-Liste

data

Der serialisierte String.

Wenn die zu deserialisierende Variable ein Objekt ist, wird PHP nach der erfolgreichen Wiederherstellung des Objekts automatisch versuchen, die __unserialize()- oder __wakeup-Methode aufzurufen (sofern eine von diesen existiert).

Hinweis: Die unserialize_callback_func-Direktive

Es ist möglich, eine Callback-Funktion anzugeben, die aufgerufen wird, wenn eine undefinierte Klasse während des Deserialisierens instanziiert werden soll (um dem Erhalt des unvollständigen Objekts "__PHP_Incomplete_Class" vorzubeugen). Nutzen Sie Ihre php.ini, ini_set() oder .htaccess, um unserialize_callback_func festzulegen. Jedesmal, wenn eine undefinierte Klasse instanziiert werden soll, wird diese Funktion aufgerufen. Um dieses Feature abzuschalten, muss die Einstellung nur ungefüllt sein.

options

Optionen, die unserialize() als assoziatives Array zur Verfügung gestellt werden sollen.

**Gültige Optionen**
Name	Typ	Beschreibung
`allowed_classes`	mixed	Entweder ein Array von Klassennamen, die akzeptiert werden sollen, oder `false` um keine Klassen oder `true` um alle Klassen zu akzeptieren. Ist diese Option angegeben und unserialize() trifft auf ein Objekt einer Klasse, die nicht akzeptierbar ist, wird das Objekt statt dessen als __PHP_Incomplete_Class instanziiert. Das Auslassen dieser Option hat die gleiche Wirkung wie sie als `true` anzugeben: PHP wird versuchen Objekte beliebiger Klassen zu instanziieren.
`max_depth`	int	Die maximale Tiefe von Strukturen, die während der Deserialisierung erlaubt ist. Diese Option soll Stack-Überläufe verhindern. Die Standardtiefe ist `4096` und kann durch Setzen von `max_depth` auf `0` deaktiviert werden.

Rückgabewerte

Der konvertierte Wert wird zurückgegeben und kann vom Typ bool, int, float, string, array oder object sein.

Falls der übergebene String nicht deserialisierbar ist, wird false zurückgegeben und E_WARNING produziert.

Fehler/Exceptions

Objekte können Throwables in ihren Deserialisierungs-Routinen ausführen.

Changelog

Version	Beschreibung
8.3.0	Gibt nun einen Fehler der Stufe `E_WARNING` aus, wenn der übergebene String nicht unserialisierbar ist; zuvor wurde ein `E_NOTICE` ausgegeben.
7.4.0	Zu `options` wurde das Element `max_depth` hinzugefügt, um die maximale Tiefe von Strukturen festzulegen, die während der Deserialisierung erlaubt ist.
7.1.0	Das `allowed_classes`-Element von `options`) ist nun strikt typisiert, d. h. wird etwas anderes als ein Array oder ein bool übergeben, liefert unserialize() `false` zurück und löst ein `E_WARNING` aus.

Beispiele

Beispiel #1 unserialize()-Beispiel

<?php
// Als Beispiel benutzen wir unserialize(), um Daten aus einer Datenbank in das
// $session_data-Array zu laden. Das Beispiel vervollständigt das unter
// serialize() beschriebene.

$conn = odbc_connect("webdb", "php", "chicken");
$stmt = odbc_prepare($conn, "SELECT data FROM sessions WHERE id = ?");
$sqldata = array($_SERVER['PHP_AUTH_USER']);
if (!odbc_execute($stmt, $sqldata) || !odbc_fetch_into($stmt, $tmp)) {
    // wenn execute oder fetch fehlschlägt, initialisiere ein leeres Array
    $session_data = array();
} else {
    // die serialisierten Daten sollten nun in $tmp[0] stehen.
    $session_data = unserialize($tmp[0]);
    if (!is_array($session_data)) {
        // etwas ging schief, also wieder ein leeres Array initialisieren
        $session_data = array();
    }
}
?>

Beispiel #2 unserialize_callback_func-Beispiel

<?php
$serialized_object='O:1:"a":1:{s:5:"value";s:3:"100";}';

ini_set('unserialize_callback_func', 'mycallback'); // Festlegen der callback_function

function mycallback($classname)
{
    // einfach eine Datei einbinden, dass die Klassendefinitionen enthält
    // Sie erhalten $classname, womit Sie herausfinden können, welche
    // Klassendefinition benötigt wird
}
?>

Anmerkungen

Warnung

false wird sowohl im Fehlerfall als auch bei einem serialisierten false-Wert zurückgegeben. Es ist möglich, diesen speziellen Fall abzufangen, indem man data mit serialize(false) vergleicht oder prüft, ob ein E_NOTICE produziert wurde.

Siehe auch

json_encode() - Liefert die JSON-Darstellung eines Wertes
json_decode() - Dekodiert eine JSON-Zeichenkette
hash_hmac() - Berechnet einen Hash mit Schlüssel unter Verwendung von HMAC
serialize() - Erzeugt eine speicherbare Repräsentation eines Wertes
Automatisches Laden von Klassen
unserialize_callback_func
unserialize_max_depth
__wakeup()
__serialize()
__unserialize()

add a note

User Contributed Notes 24 notes

down

103

me+phpnet at unreal4u dot com ¶

7 years ago


Just some reminder which may save somebody some time regarding the `$options` array: 

Say you want to be on the safe side and not allow any objects to be unserialized... My first thought was doing the following:

<?php
$lol = unserialize($string, false);
// This will generate:
// Warning: unserialize() expects parameter 2 to be array, boolean given
?>

The correct way of doing this is the following:
<?php
$lol = unserialize($string, ['allowed_classes' => false]);
?>

Hope it helps somebody!

down

karsten at dambekalns dot de ¶

3 years ago


Keep in mind that the allowed_classes does not use inheritance, i.e. allowing an interface is not possible and sub-classes won't pass the check. See https://3v4l.org/tdHfl

down

ErnestV ¶

11 years ago


Just a note - if the serialized string contains a reference to a class that cannot be instantiated (e.g. being abstract) PHP will immediately die with a fatal error. If the unserialize() statement is preceded with a '@' to avoid cluttering the logs with warns or notices there will be absolutely no clue as to why the script stopped working. Cost me a couple of hours...

down

daniel at fourstaples dot com ¶

14 years ago


Here's a simple function to get the class of a serialized string (that is, the type of object that will be returned if it's unserialized):

<?php
function get_serial_class($serial) {
    $types = array('s' => 'string', 'a' => 'array', 'b' => 'bool', 'i' => 'int', 'd' => 'float', 'N;' => 'NULL');
    
    $parts = explode(':', $serial, 4);
    return isset($types[$parts[0]]) ? $types[$parts[0]] : trim($parts[2], '"'); 
}
?>

I use this when saving a serialized object to a cookie, to make sure it is the right type when I go to unserialize it.

The type names are the same format/case as you would see if you did a var_dump().

down

hadley8899 at gmail dot com ¶

4 years ago


For the people who are getting the error 

PHP Notice:  unserialize(): Error at offset 191 of 285 bytes in ...

and are getting the data from a database, Make sure that you have the database set the the correct encoding, I had the database set as latin1_swedish_ci and all of the data looked perfect, Infact when i copied it into a online unserialize it worked fine. I changed the collation to utf8mb4_unicode_ci and all worked fine.

down

bjd ¶

7 years ago


Talk on Exploiting PHP7 Unserialize here: https://media.ccc.de/v/33c3-7858-exploiting_php7_unserialize

down

chris at pollett dot org ¶

9 years ago


When you serialize an object of a class from a particular namespace, the namespace is recorded as part of the serialization. If you decide to change this namespace's name, it can be hard to read in old serialized objects. I.e., suppose you had serialized an object of type foo\A, you change the namespace of your project to goo but otherwise leave the class definition of A unchanged. You would like to be able to unserialize the object as goo\A, instead unserialization will only create a partial object. To fix this in the case where you don't have nested objects in your class definition, you can use the following simple rename function:
/**
 * Used to change the namespace of a serialized php object (assumes doesn't
 * have nested subobjects)
 *
 * @param string $class_name new fully qualified name with namespace
 * @param string $object_string serialized object
 *
 * @return string serialized object with new name
 */
function renameSerializedObject($class_name, $object_string)
{
    /*  number of digits in the length of name of the object needs to be 
        less than 12 digits (probably more like 4) for this to work.
    */
    $name_length = intval(substr($object_string, 2, 14));
    $name_space_info_length = strlen("O:".$name_length.":") +
        $name_length + 2; // 2 for quotes;
    $object_string = 'O:' .
        strlen($class_name) . ':"'. $class_name.'"' .
        substr($object_string, $name_space_info_length);
    return $object_string;
}

down

Ray.Paseur often uses Gmail ¶

11 years ago


In the Classes and Objects docs, there is this: In order to be able to unserialize() an object, the class of that object needs to be defined.

Prior to PHP 5.3, this was not an issue.  But after PHP 5.3 an object made by SimpleXML_Load_String() cannot be serialized.  An attempt to do so will result in a run-time failure, throwing an exception.  If you store such an object in $_SESSION, you will get a post-execution error that says this:

Fatal error: Uncaught exception 'Exception' with message 'Serialization of 'SimpleXMLElement' is not allowed' in [no active file]:0 Stack trace: #0 {main} thrown in [no active file] on line 0

The entire contents of the session will be lost.  Hope this saves someone some time!

<?php // RAY_temp_ser.php
error_reporting(E_ALL);
session_start();
var_dump($_SESSION);
$_SESSION['hello'] = 'World';
var_dump($_SESSION);

// AN XML STRING FOR TEST DATA
$xml = '<?xml version="1.0"?>
<families>
  <parent>
    <child index="1" value="Category 1">Child One</child>
  </parent>
</families>';

// MAKE AN OBJECT (GIVES SimpleXMLElement)
$obj = SimpleXML_Load_String($xml);

// STORE THE OBJECT IN THE SESSION
$_SESSION['obj'] = $obj;

down

arbie samong ¶

15 years ago


__PHP_Incomplete_Class Object Demystified



1. First take note of the output. A simple example:



__PHP_Incomplete_Class Object (

[__PHP_Incomplete_Class_Name] => SomeObject1

[obj1property1] => somevalue1 [obj1property2] => __PHP_Incomplete_Class Object ( [__PHP_Incomplete_Class_Name] => SomeObject2 [obj2property1] => somevalue1 [obj2property2] => Array (

['key1'] => somevalue3, ['key2'] => somevalue4 ) ) )



2. We analyze this and break it down. 

__PHP_Incomplete_Class Object tells you there is an object that needs to be declared somehow. 

__PHP_Incomplete_Class_Name simply tells you the expected class name. It is just one of the properties for now.



So we have:

a) an unknown object that has a class name SomeObject1 (first class)

b) it has 2 properties, namely obj1property1 and obj2property2

c) obj2property2 is itself an object whose class name is SomeObject2 (the second class)

d) SomeObject2 has two properties, obj2property1 and obj2property2

e) obj2property2 is an array that contains two elements



3. Now that we have an idea of the structure, we shall create class definitions based from it. We will just create properties for now, methods are not required as a minimum.



<?php

class SomeObject1 {

        public $obj1property1;

        public $obj1property2;

}

class SomeObject2 {

        public $obj2property1;

        public $obj2property2;

}

?>



4. Have that accessible to your script and it will solve the __PHP_Incomplete_Class Object problem as far as the output is concerned. Now you will have:



SomeObject1 ( [obj1property1] => somevalue1 [obj1property2] => SomeObject2 ( [obj2property1] => somevalue1 [obj2property2] => Array ( ['key1'] => somevalue3, ['key2'] => somevalue4 ) ) )



As you will notice, __PHP_Incomplete_Class Object is gone and replaced by the class name. The property __PHP_Incomplete_Class_Name is also removed.



5. As for the array property obj2property2, we can directly access that and just assume that it is an array and loop through it:



<?php



// this will be SomeObject1 

$data = unserialize($serialized_data);



// this will be SomeObject2

$data2 = $data->obj1property2();



foreach($data2->obj2property2 as $key => $value):

         print $key.' : '. $value .'<br>'; 

endforeach;



?>



Outputs:

key1 : somevalue3

key2 : somevalue4



That's it. You can add more methods on the class declarations for the given properties, provided you keep your original output as basis for the data types.

down

m.m.j.kronenburg ¶

8 years ago


You can use the following code to use the php 7 unserialize function in php 5.3 and upwards. This adds the $option argument.

<?php

namespace
{

/**
 * PHP 7 unserialize function for PHP 5.3 upwards.
 * Added the $option argument (allowed_classes).
 * See php unserialize manual for more detail.
 **/
function php7_unserialize($str, $options = array())
{
  if(version_compare(PHP_VERSION, '7.0.0', '>='))
  { return unserialize($str, $options); }

  $allowed_classes = isset($options['allowed_classes']) ? 
    $options['allowed_classes'] : true;
  if(is_array($allowed_classes) || !$allowed_classes)
  {
    $str = preg_replace_callback(
      '/(?=^|:)(O|C):\d+:"([^"]*)":(\d+):{/', 
      function($matches) use ($allowed_classes)
      {
        if(is_array($allowed_classes) && 
          in_array($matches[2], $allowed_classes))
        { return $matches[0]; }
        else
        {
          return $matches[1].':22:"__PHP_Incomplete_Class":'.
            ($matches[3] + 1).
            ':{s:27:"__PHP_Incomplete_Class_Name";'.
            serialize($matches[2]);
        }
      },
      $str
    );
  }
  unset($allowed_classes);
  return unserialize($str);
}

} // namespace

namespace my_name_space
{
  /**
   * Use the new php7 unserialize in your namespace without
   * renaming all unserialize(...) function calls to 
   * php7_unserialize(...).
   **/
  function unserialize($str, $options = array())
  { return php7_unserialize($str, $options); }
}

?>

down

chris AT cmbuckley DOT co DOT uk ¶

16 years ago


As mentioned in the notes, unserialize returns false in the event of an error and for boolean false. Here is the first solution mentioned, without using error handling:

<?php
function isSerialized($str) {
    return ($str == serialize(false) || @unserialize($str) !== false);
}

var_dump(isSerialized('s:6:"foobar";')); // bool(true)
var_dump(isSerialized('foobar'));        // bool(false)
var_dump(isSerialized('b:0;'));          // bool(true)
?>

down

w dot laurencine at teknoa dot net ¶

15 years ago


When dealing with a string which contain "\r", it seems that the length is not evaluated correctly. The following solves the problem for me :

<?php
// remove the \r caracters from the $unserialized string
$unserialized = str_replace("\r","",$unserialized);

// and then unserialize()
unserialize($unserialized);
?>

down

chris at colourlovers dot com ¶

13 years ago


Anyone having trouble serializing data with SimpleXMLElement objects stored within it, check this out:

This will traverse $data looking for any children which are instances of SimpleXMLElement, and will run ->asXML() on them, turning them into a string and making them serializable. Other data will be left alone.

<?php
function exportNestedSimpleXML($data) {
    if (is_scalar($data) === false) {
        foreach ($data as $k => $v) {
            if ($v instanceof SimpleXMLElement) {
                $v = str_replace("&#13;","\r",$v->asXML());
            } else {
                $v = exportNestedSimpleXML($v);
            }

            if (is_array($data)) {
                $data[$k] = $v;
            } else if (is_object($data)) {
                $data->$k = $v;
            }
        }
    }

    return $data;
}

$data = array (
    "baz" => array (
        "foo" => new stdClass(),
        "int" => 123,
        "str" => "asdf",
        "bar" => new SimpleXMLElement('<?xml version="1.0" encoding="UTF-8"?><foo>bar</foo>'),
    )
);

var_dump($data);
/*array(1) {
  ["baz"]=>
  array(4) {
    ["foo"]=>
    object(stdClass)#3 (0) {
    }
    ["int"]=>
    int(123)
    ["str"]=>
    string(4) "asdf"
    ["bar"]=>
    object(SimpleXMLElement)#4 (1) {
      [0]=>
      string(3) "bar"
    }
  }
}*/

var_dump(exportNestedSimpleXML($data));
/*array(1) {
  ["baz"]=>
  array(4) {
    ["foo"]=>
    object(stdClass)#3 (0) {
    }
    ["int"]=>
    int(123)
    ["str"]=>
    string(4) "asdf"
    ["bar"]=>
    string(54) "<?xml version="1.0" encoding="UTF-8"?>
<foo>bar</foo>
"
  }
}
*/
?>

down

BenBE at omorphia dot de ¶

17 years ago


When trying to serialize or unserialize recursive arrays or otherwise linked data you might find the undocumented R data type quite useful.

If you want a array like the one produced with
<?
$a = array();
$a[0] =& $a;
?>
serialized you can store it using a string simular to this one:
<?
$a = unserialize("a:1:{i:0;R:1;}");
?>

Both sources will make $a hold an array that self-references itself in index 0.

The argument for R is the index of the created sub-variable of the serialize-string beginning with 1.

down

Are Pedersen ¶

18 years ago


Be aware that if useing serialize/unserialize in a serverfarm with both 32bit and 64bit servers you can get unexpected results.

Ex: if you serialize an integer with value of 2147483648 on a 64bit system and then unserialize it on a 32bit system you will get the value -2147483648 instead. This is because an integer on 32bit cannot be above 2147483647 so it wraps.

down

double at dumpit dot com ¶

17 years ago


This little function will check whether the serialized string is well formed. 

PHP < 6 because i'd heard changes will be made in this php-intern function, 
maybe it could be edited easy for it.

<?php

function wd_check_serialization( $string, &$errmsg ) 
{

    $str = 's';
    $array = 'a';
    $integer = 'i';
    $any = '[^}]*?';
    $count = '\d+';
    $content = '"(?:\\\";|.)*?";';
    $open_tag = '\{';
    $close_tag = '\}';
    $parameter = "($str|$array|$integer|$any):($count)" . "(?:[:]($open_tag|$content)|[;])";            
    $preg = "/$parameter|($close_tag)/";
    if( !preg_match_all( $preg, $string, $matches ) ) 
    {            
        $errmsg = 'not a serialized string';
        return false;
    }    
    $open_arrays = 0;
    foreach( $matches[1] AS $key => $value )
    {
        if( !empty( $value ) && ( $value != $array xor $value != $str xor $value != $integer ) ) 
        {
            $errmsg = 'undefined datatype';
            return false;
        }
        if( $value == $array )
        {
            $open_arrays++;                                
            if( $matches[3][$key] != '{' ) 
            {
                $errmsg = 'open tag expected';
                return false;
            }
        }
        if( $value == '' )
        {
            if( $matches[4][$key] != '}' ) 
            {
                $errmsg = 'close tag expected';
                return false;
            }
            $open_arrays--;
        }
        if( $value == $str )
        {
            $aVar = ltrim( $matches[3][$key], '"' );
            $aVar = rtrim( $aVar, '";' );
            if( strlen( $aVar ) != $matches[2][$key] ) 
            {
                $errmsg = 'stringlen for string not match';
                return false;
            }
        }
        if( $value == $integer )
        {
            if( !empty( $matches[3][$key] ) ) 
            {
                $errmsg = 'unexpected data';
                return false;
            }
            if( !is_integer( (int)$matches[2][$key] ) ) 
            {
                $errmsg = 'integer expected';
                return false;
            }
        }
    }        
    if( $open_arrays != 0 ) 
    {
        $errmsg = 'wrong setted arrays';
        return false;
    }
    return true;
}

?>

down

-1

OscarZarrus ¶

2 years ago


For those who are looking for an efficient solution for handling controversial "FALSE", they can use this function which in case of non-unserializable string, instead of a "FALSE", throws an Exception. Vice versa it returns the unserialized variable.

<?php

    /**

     * @param string $serializedString

     * @param array $options

     * @return mixed

     * @throws Exception

     */

    function UnSerialize(string $serializedString, array $options = []) {

        $_unserialized = @unserialize($serializedString, $options);

        if ($serializedString === serialize(false) || $_unserialized !== false){

            return $_unserialized;

        }

        throw new Exception("Non-unserializable string");



    }



?>

down

Chris Hayes (chris at hypersites dot com) ¶

20 years ago


In reply to the earlier post about having to include object definitions *before* using unserialize.  There is a workaround for this.

When an object is serialized, the first bit of the string is actually the name of the class.  When an unknown object is unserialized, this is maintained as a property.  So if you serialize it again, you get back the exact same string as if you'd serialized the original object.  Basically, to cut to the point...

If you use

$_SESSION['my_object'] = unserialize(serialize($_SESSION['my_object']))

then you get back an object of the correct type, even if the session had originally loaded it as an object of type stdClass.

down

suman dot jis at gmail dot com ¶

12 years ago


I was getting unserialize()  Error at offset error.

If you face similar problem  then use the following procedure

$auctionDetails = preg_replace('!s:(\d+):"(.*?)";!se', "'s:'.strlen('$2').':\"$2\";'", $dataArr[$i]['auction_details'] ); 
$auctionDetails = unserialize($auctionDetails);

down

-3

aderyn at nowhere dot tld ¶

21 years ago


A quick note:
If you store a serialized object in a session, you have to include the class _before_ you initialize (session_start()) the session.

down

-3

Anonymous ¶

5 years ago


If serialize() is the answer, you're almost certainly asking the wrong question.

JSON is widely available. The only thing it does not do, is the very thing that makes serialization immensely dangerous. All it takes is a crafty hacker to pass a crafted payload to a supposedly 'secured' serialize call, for a database driver to be overwritten with malicious code, for example.

Recreate the object. Normally. With actual data, and a source file, not with serialize. To do otherwise is laziness bordering on malice.

down

-6

MBa ¶

13 years ago


To check if a string is serialized:

$blSerialized=(@unserialize($sText)||$sText=='b:0;');

down

-6

walf ¶

13 years ago


a replacement for unserialize that returns whether it worked and populates the unserialized variable by reference:
<?php
function funserialize($serialized, &$into) {
    static $sfalse;
    if ($sfalse === null)
        $sfalse = serialize(false);
    $into = @unserialize($serialized);
    return $into !== false || rtrim($serialized) === $sfalse;//whitespace at end of serialized var is ignored by PHP
}

$s_foo = 'b:0;';
var_dump(funserialize($s_foo, $foo), $foo);

$s_bar = 'bar';
var_dump(funserialize($s_bar, $bar), $bar);

$s_foo = 'a:0:{};';
var_dump(funserialize($s_foo, $foo), $foo);

?>
gives:

bool(true)
bool(false)

bool(false)
bool(false)

bool(true)
array(0) {
}

down

-11

Fagzal ¶

14 years ago


To all who have problem with quoting and slashes when storing serialized data in MySQL: you are probably doing it wrong.

Use e.g. PDO with placeholders and the blob column type, and it will Just Work.

add a note