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 an integer, float, string, array or object. In case the passed string is not unserializeable, FALSE is returned.
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. PHP 4 removes that limitation and restores both properties and methods. 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().
