PHP5 PDO Singleton Class

$dbObj =& new sdb("mysql:host=localhost;dbname=testdb", 'username', 'password');

<?php

/**
 * PDO SINGLETON CLASS
 *
 * @author Tony Landis
 * @link
 * @license Use how you like it, just please don't remove or alter this PHPDoc
 */
class sdb
{
    /**
     * The singleton instance
     *
     */
    static private $PDOInstance;

      /**
       * Creates a PDO instance representing a connection to a database and makes the instance available as a singleton
       *
       * @param string $dsn The full DSN, eg: mysql:host=localhost;dbname=testdb
       * @param string $username The user name for the DSN string. This parameter is optional for some PDO drivers.
       * @param string $password The password for the DSN string. This parameter is optional for some PDO drivers.
       * @param array $driver_options A key=>value array of driver-specific connection options
       *
       * @return PDO
       */
    public function __construct($dsn, $username=false, $password=false, $driver_options=false)
    {
        if(!self::$PDOInstance) {
            try {
               self::$PDOInstance = new PDO($dsn, $username, $password, $driver_options);
            } catch (PDOException $e) {
               die("PDO CONNECTION ERROR: " . $e->getMessage() . "");
            }
        }
          return self::$PDOInstance;
    }

      /**
       * Initiates a transaction
       *
       * @return bool
       */
    public function beginTransaction() {
        return self::$PDOInstance->beginTransaction();
    }

    /**
     * Commits a transaction
     *
     * @return bool
     */
    public function commit() {
        return self::$PDOInstance->commit();
    }

    /**
     * Fetch the SQLSTATE associated with the last operation on the database handle
     *
     * @return string
     */
    public function errorCode() {
        return self::$PDOInstance->errorCode();
    }

    /**
     * Fetch extended error information associated with the last operation on the database handle
     *
     * @return array
     */
    public function errorInfo() {
        return self::$PDOInstance->errorInfo();
    }

    /**
     * Execute an SQL statement and return the number of affected rows
     *
     * @param string $statement
     */
    public function exec($statement) {
        return self::$PDOInstance->exec($statement);
    }

    /**
     * Retrieve a database connection attribute
     *
     * @param int $attribute
     * @return mixed
     */
    public function getAttribute($attribute) {
        return self::$PDOInstance->getAttribute($attribute);
    }

    /**
     * Return an array of available PDO drivers
     *
     * @return array
     */
    public function getAvailableDrivers(){
        return Self::$PDOInstance->getAvailableDrivers();
    }

    /**
     * Returns the ID of the last inserted row or sequence value
     *
     * @param string $name Name of the sequence object from which the ID should be returned.
     * @return string
     */
    public function lastInsertId($name) {
        return self::$PDOInstance->lastInsertId($name);
    }

       /**
     * Prepares a statement for execution and returns a statement object
     *
     * @param string $statement A valid SQL statement for the target database server
     * @param array $driver_options Array of one or more key=>value pairs to set attribute values for the PDOStatement obj
returned
     * @return PDOStatement
     */
    public function prepare ($statement, $driver_options=false) {
        if(!$driver_options) $driver_options=array();
        return self::$PDOInstance->prepare($statement, $driver_options);
    }

    /**
     * Executes an SQL statement, returning a result set as a PDOStatement object
     *
     * @param string $statement
     * @return PDOStatement
     */
    public function query($statement) {
        return self::$PDOInstance->query($statement);
    }

    /**
     * Execute query and return all rows in assoc array
     *
     * @param string $statement
     * @return array
     */
    public function queryFetchAllAssoc($statement) {
        return self::$PDOInstance->query($statement)->fetchAll(PDO::FETCH_ASSOC);
    }

    /**
     * Execute query and return one row in assoc array
     *
     * @param string $statement
     * @return array
     */
    public function queryFetchRowAssoc($statement) {
        return self::$PDOInstance->query($statement)->fetch(PDO::FETCH_ASSOC);
    }

    /**
     * Execute query and select one column only
     *
     * @param string $statement
     * @return mixed
     */
    public function queryFetchColAssoc($statement) {
        return self::$PDOInstance->query($statement)->fetchColumn();
    }

    /**
     * Quotes a string for use in a query
     *
     * @param string $input
     * @param int $parameter_type
     * @return string
     */
    public function quote ($input, $parameter_type=0) {
        return self::$PDOInstance->quote($input, $parameter_type);
    }

    /**
     * Rolls back a transaction
     *
     * @return bool
     */
    public function rollBack() {
        return self::$PDOInstance->rollBack();
    }

    /**
     * Set an attribute
     *
     * @param int $attribute
     * @param mixed $value
     * @return bool
     */
    public function setAttribute($attribute, $value  ) {
        return self::$PDOInstance->setAttribute($attribute, $value);
    }
}
?>