PHP Manual: unserialize

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();
    }
}
?>