Description:
------------
When i try to override PDO_Statement::execute(), my Method is ignored completly.

When i try to implement ::foo() in my extending class, PHP states it is undefined.

Reproduce code:
---------------
<?php

class MTFrame_DB_PDOStatement extends PDOStatement
{

    public function execute()
    {
        throw new Exception();
        // Nothing happens, i'm ignored
    }

    public function foo()
    {
        throw new Exception();
        // i do not exist?
    }
}

class MTFrame_DB_PDO extends PDO
{
    function prepare($sql)
    {
        return parent::prepare($sql, array(PDO_ATTR_STATEMENT_CLASS=>array('MTFrame_DB_PDOStatement')));
    }
    
    function query($sql)
    {
        $stmt = parent::prepare($sql, array(PDO_ATTR_STATEMENT_CLASS=>array('MTFrame_DB_PDOStatement')));
        $stmt->foo();
        return $stmt;
    }
}

?>

Actual result:
--------------
MTFrame_DB_PDOStatement::execute() gets ignored.

calling ::foo() produces:
Call to undefined method MTFrame_DB_PDOStatement::foo()