(PHP 4, PHP 5, PHP 7)
unserialize — Creates a PHP value from a stored representation
unserialize() takes a single serialized variable and converts it back into a PHP value.
strThe serialized string.
If the variable being unserialized is an object, after successfully reconstructing the object PHP will automatically attempt to call the __wakeup() member function (if it exists).
Note: unserialize_callback_func directive
It's possible to set a callback-function which will be called, if an undefined class should be instantiated during unserializing. (to prevent getting an incomplete object "__PHP_Incomplete_Class".) Use your php.ini, ini_set() or .htaccess to define 'unserialize_callback_func'. Everytime an undefined class should be instantiated, it'll be called. To disable this feature just empty this setting.
optionsAny options to be provided to unserialize(), as an associative array.
| Name | Type | Description |
|---|---|---|
| allowed_classes | mixed |
Either an array of class names which should be
accepted, FALSE to accept no classes, or TRUE to accept all
classes. If this option is defined and
unserialize() encounters an object of a class
that isn't to be accepted, then the object will be instantiated as
__PHP_Incomplete_Class instead.
Omitting this option is the same as defining it as TRUE: PHP
will attempt to instantiate objects of any class.
|
The converted value is returned, and can be a boolean, integer, float, string, array or object.
In case the passed string is not unserializeable, FALSE is returned and
E_NOTICE is issued.
| Version | Description |
|---|---|
| 7.0.0 |
The options parameter has been added.
|
| 5.6.0 | Manipulating the serialised data by replacing C: with O: to force object instantiation without calling the constructor will now fail. |
Example #1 unserialize() example
<?php
// Here, we use unserialize() to load session data to the
// $session_data array from the string selected from a database.
// This example complements the one described with serialize().
$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)) {
// if the execute or fetch fails, initialize to empty array
$session_data = array();
} else {
// we should now have the serialized data in $tmp[0].
$session_data = unserialize($tmp[0]);
if (!is_array($session_data)) {
// something went wrong, initialize to empty array
$session_data = array();
}
}
?>
Example #2 unserialize_callback_func example
<?php
$serialized_object='O:1:"a":1:{s:5:"value";s:3:"100";}';
// unserialize_callback_func directive available as of PHP 4.2.0
ini_set('unserialize_callback_func', 'mycallback'); // set your callback_function
function mycallback($classname)
{
// just include a file containing your classdefinition
// you get $classname to figure out which classdefinition is required
}
?>
FALSE is returned both in the case of an error and if unserializing
the serialized FALSE value. It is possible to catch this special case by
comparing str with
serialize(false) or by catching the issued
E_NOTICE.
Do not pass untrusted user input to unserialize(). Unserialization can result in code being loaded and executed due to object instantiation and autoloading, and a malicious user may be able to exploit this. Use a safe, standard data interchange format such as JSON (via json_decode() and json_encode()) if you need to pass serialized data to the user.
As mentioned in the notes, unserialize returns false in the event of an error and for boolean false. Here is the first solution mentioned, without using error handling:
<?php
function isSerialized($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)
?>
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...
__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.
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;
}
?>
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'] = $obj;
Here's a simple function to get the class of a serialized string (that is, the type of object that will be returned if it's unserialized):
<?php
function get_serial_class($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().
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;
}
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);
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) {
$v = str_replace(" ","\r",$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>
"
}
}
*/
?>
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.
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);
?>
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.
When you use sessions, its very important to keep the sessiondata small, due to low performance with unserialize. Every class shoud extend from this class. The result will be, that no null Values are written to the sessiondata. It will increase performance.
<?
class BaseObject
{
function __sleep()
{
$vars = (array)$this;
foreach ($vars as $key => $val)
{
if (is_null($val))
{
unset($vars[$key]);
}
}
return array_keys($vars);
}
};
?>
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.
I faced with error when serializing/deserializing an object. The error looks like
Notice: unserialize(): Error at offset 2 of 52 bytes in file.php on line 130
and found solution here: http://davidwalsh.name/php-serialize-unserialize-issues
The safe way to serialize and unserialize:
//to safely serialize
$serialized = base64_encode(serialize($var));
//to unserialize...
$unserialized = unserialize(base64_decode($var));
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) {
}
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.
To check if a string is serialized:
$blSerialized=(@unserialize($sText)||$sText=='b:0;');
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 $a hold an array that self-references itself in index 0.
The argument for R is the index of the created sub-variable of the serialize-string beginning with 1.
When unserializing in PHP5 (behavior observed with 5.1.2), __autoload() will be checked first, and unserialize_callback_func called only if __autoload failed to load the class definition.
When dealing with sessions, try session_decode($data) instead of unserialize($data).
If instead of using JSON, you'd like to stick with PHP-style serialization, here's some JavaScript code I posted at http://magnetiq.com for serializing JavaScript objects in PHP fashion:
/* Returns the class name of the argument or undefined if
it's not a valid JavaScript object.
*/
function getObjectClass(obj)
{
if (obj && obj.constructor && obj.constructor.toString)
{
var arr = obj.constructor.toString().match(
/function\s*(\w+)/);
if (arr && arr.length == 2)
{
return arr[1];
}
}
return undefined;
}
/* Serializes the given argument, PHP-style.
The type mapping is as follows:
JavaScript Type PHP Type
--------------- --------
Number Integer or Decimal
String String
Boolean Boolean
Array Array
Object Object
undefined Null
The special JavaScript object null also becomes PHP Null.
This function may not handle associative arrays or array
objects with additional properties well.
*/
function phpSerialize(val)
{
switch (typeof(val))
{
case "number":
return (Math.floor(val) == val ? "i" : "d") + ":" +
val + ";";
case "string":
return "s:" + val.length + ":\"" + val + "\";";
case "boolean":
return "b:" + (val ? "1" : "0") + ";";
case "object":
if (val == null)
{
return "N;";
}
else if ("length" in val)
{
var idxobj = { idx: -1 };
return "a:" + val.length + ":{" + val.map(
function (item)
{
this.idx++;
var ser = phpSerialize(item);
return ser ?
phpSerialize(this.idx) + ser :
false;
}, idxobj).filter(
function (item)
{
return item;
}).join("") + "}";
}
else
{
var class_name = getObjectClass(val);
if (class_name == undefined)
{
return false;
}
var props = new Array();
for (var prop in val)
{
var ser = phpSerialize(val[prop]);
if (ser)
{
props.push(phpSerialize(prop) + ser);
}
}
return "O:" + class_name.length + ":\"" +
class_name + "\":" + props.length + ":{" +
props.join("") + "}";
}
case "undefined":
return "N;";
}
return false;
}
On the client side, you can pass in a complex (nested) JavaScript object to the phpSerialize function to get a PHP-style serialized representation. This string can be posted back and directly passed to the unserialize function to yield a representation of the complex object in PHP realm. Use of this technique requires caution on security matters.
