Description:
------------
It throw a error when execute a PDO's instance in the 'run' of Pthreads's method.

Fatal error: Uncaught exception 'PDOException' with message 'You cannot serialize or unserialize PDO instances' 

Test script:
---------------
class Async extends Thread
{

    /**
     * Provide a passthrough to call_user_func_array
     * */
    public function __construct($method, $params)
    {
        $this->method = $method;
        $this->params = $params;
        $this->result = null;
        $this->joined = false;
    }

    /**
     * The smallest thread in the world
     * */
    public function run()
    {
        $this->result=call_user_func_array($this->method, $this->params);
    }

    /**
     * Static method to create your threads from functions ...
     * */
    public static function call($method, $params)
    {
        $thread = new Async($method, $params);
        if ($thread->start()) {
            return $thread;
        } /** else throw Nastyness * */
    } 

}

class test
{

    public $dbh;

    public function __construct()
    {
        $dsn = 'mysql:dbname=mysql;host=127.0.0.1';
        $user = 'root';
        $password = '123456';
        $this->dbh = new PDO($dsn, $user, $password);
    }

    public function world()
    {
        $sql = 'SELECT * FROM user ';
        foreach ($this->dbh->query($sql) as $row) {
            print $row['User'] . "\t";
        }
    }

}

$cc = new test;

/* here's us calling file_get_contents in a thread of it's own */
$future = Async::call(array($cc, 'world'), array());

Expected result:
----------------
error

Actual result:
--------------
no error