将PDO连接作为会话变量传递

Question

So in the interest of not repeating myself, I only want to create one PDO connection and pass it between pages using a session var. But when I setup my PDO connection and set the session var, the var is coming back as not set on my next page?

This is the code on my first page:

session_start();
try
{
    $db = new PDO("mysql:host=".$dbHostname.";dbname=".$dbDatabase, $dbUsername, $dbPassword);
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $e)
{
    echo "It seems there was an error.  Please refresh your browser and try again. ".$e->getMessage();
}

$_SESSION['db'] = $db;

Then this test code on my next page comes back as not set.

session_start();
$db = $_SESSION['db'];

    if(isset($db))echo "set";
    else echo "not set";

Any ideas??

The connection is fine because if I call a function from the first page and pass along $db as a parameter, the function works without any problems. So why would storing the database var as a session not work? Thank you for any help.

Answer 1

PDO does not allow session serialization. In fact, you should not be able to serialize database connections in the session at all. If it's really necessary to do that, you can do something like this:

class DB {
   private $db;
   private $creds;

   public function __construct($host, $dbname, $user, $pass) {
      $this->creds = compact('host', 'dbname', 'user', 'pass');
      $this->db = self::createLink($host, $dbname, $user, $pass);
   }

   public function __sleep() {
      return array('creds');
   }

   public function __wakeup() {
      $this->db = self::createLink($this->creds['host'] ...
   }

   public static function createLink($host ...
      return new PDO(...
   }
}