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# unserialize

(PHP 3 >= 3.0.5, PHP 4, PHP 5)

unserialize -- Creates a PHP value from a stored representation

## Description

mixed unserialize ( string str )

unserialize() takes a single serialized variable (see serialize()) and converts it back into a PHP value. 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.

Warning
`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.

> 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. Also note that the directive unserialize_callback_func directive became available in PHP 4.2.0.

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).

Example 1. 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 } ?>`

> Note: In PHP 3, methods are not preserved when unserializing a serialized object. That limitation was removed in PHP 4 as both properties and methods are now restored. Please see the Serializing Objects section of Classes and Objects or more information.

Example 2. 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 = ?"); $sqldata = array ($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(); } } ?>`

See also serialize().

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