Description:
------------
I'm getting the following error when the ATTR_STATEMENT_CLASS option is set...

Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000]: General error: PDO::ATTR_STATEMENT_CLASS requires format array(classname, array(ctor_args)); the classname must be a string specifying an existing class' in ..../drupal7/includes/database/database.inc:338

The same configuration works for PHP 5.2 and 5.3

The reproduce code is the constructor of the DatabaseConnection class of Drupal 7, see also http://cvs.drupal.org/viewvc.py/drupal/drupal/includes/database/database.inc?revision=1.57&view=markup

Reproduce code:
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  function __construct($dsn, $username, $password, $driver_options = array()) {
    // Because the other methods don't seem to work right.
    $driver_options[PDO::ATTR_ERRMODE] = PDO::ERRMODE_EXCEPTION;

    // Call PDO::__construct and PDO::setAttribute.
    parent::__construct($dsn, $username, $password, $driver_options);

    // Set a specific PDOStatement class if the driver requires that.
    if (!empty($this->statementClass)) {
      $this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array($this->statementClass, array($this)));
    }
  }


Expected result:
----------------
The connection can be established....

Actual result:
--------------
Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000]: General error: PDO::ATTR_STATEMENT_CLASS requires format array(classname, array(ctor_args)); the classname must be a string specifying an existing class' in ..../drupal7/includes/database/database.inc:338
Stack trace:
#0 .../drupal7/includes/database/database.inc(338): PDO->setAttribute(13, Array)
#1 .../drupal7/includes/database/mysql/database.inc(36): DatabaseConnection->__construct('mysql:host=loca...', 'd7', 'd7', Array)
#2 /.../drupal7/includes/database/database.inc(1350): DatabaseConnection_mysql->__construct(Array)
#3 .../drupal7/includes/database/database.inc(1218): Database::openConnection('default', 'default')
#4 .../drupal7/includes/database/database.inc(1793): Database::getConnection('default')
#5 .../drupal7/includes/bootstrap.inc(1242): db_query('SELECT 1 FROM {...', Array)