Below is an example of extending PDO & PDOStatement classes:

<?php

class Database extends PDO
{
    function __construct()
    {
        parent::__construct('mysql:dbname=test;host=localhost', 'root', '');
        $this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array('DBStatement', array($this)));
    }
}

class DBStatement extends PDOStatement
{
    public $dbh;

    protected function __construct($dbh)
    {
        $this->dbh = $dbh;
        $this->setFetchMode(PDO::FETCH_OBJ);
    }
    
    public function foundRows()
    {
        $rows = $this->dbh->prepare('SELECT found_rows() AS rows', array(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => TRUE));
        $rows->execute();
        $rowsCount = $rows->fetch(PDO::FETCH_OBJ)->rows;
        $rows->closeCursor();
        return $rowsCount;
    }
}

?>