Model.class.php

<?php
    class Model {
        protected static function db() {
            return DatabasePDO::singleton();
        }

        // *** Queries in sql/model.sql.php ****
        protected static $requests = array();

        public static function addSqlQuery($key, $sql) {
            static::$requests[$key] = $sql;
        }

        public static function sqlQueryNamed($key) {
            return static::$requests[$key];
        }

        protected static function query($sql) {
            $st = static::db()->query($sql)  or die("sql query error ! request : " . $sql);
            $st->setFetchMode(PDO::FETCH_CLASS | PDO::FETCH_PROPS_LATE, get_called_class());
            return $st;
        }

        protected static function exec($sqlKey, $values=array()) {
            $sth = static::db()->prepare(static::sqlQueryNamed($sqlKey));
            $sth->setFetchMode(PDO::FETCH_CLASS | PDO::FETCH_PROPS_LATE, get_called_class());
            $sth->execute($values);
            return $sth;
        }
    }
?>