How can I pass DB connection object from one class to another? - php

Question

I'm trying to pass a PDO connection object from one class to another. But I'm not being very successfull. And I only want to instanciate only one PDO object.
With the help from dqhendricks and awm I managed to get the following solution working:
class Factory {
function createUser($id = NULL) {
return new User(Conn::get_conn(), $id);
}
function createApplication($id = NULL) {
return new User(Conn::get_conn(), $id);
}
}
class Conn {
private static $conn = NULL;
private function __construct() {}
private static function init() {
$conf = self::config();
try {
self::$conn = new PDO($conf['dsn'], $conf['user'], $conf['pass']);
}
catch (PDOException $e) {
echo $e->getMessage();
}
}
public static function get_conn() {
if (!self::$conn) { self::init(); }
return self::$conn;
}
private static function config($cfg_file = 'sl.config') {
$config = parse_ini_file('/../'.$cfg_file);
$conf = array();
$conf['user'] = $config['db_user'];
$conf['pass'] = $config['db_password'];
$conf['dsn'] = 'mysql:dbname='.$config['db_name'].';host='.$config['db_host'];
return $conf;
}
}
In my UserDAO class, I can now do this:
class UserDAO {
private $db;
private $id;
function UserDAO (&$db, $id) {
$this->db = &$db;
$this->id = &$id;
}
public function getRows($sql)
{
$result = $this->db->query($sql);
$row = $result->fetch(PDO::FETCH_ASSOC);
return $row;
}
function getUsers($limit = 10) {
$sql ="SELECT * FROM sl_store LIMIT $limit";
return $this->getRows($sql);
}
}
//My User class
class User extends UserDAO implements iUser {}
// And to test it working:
$user1 = Factory::createUser('5');
$user2 = Factory::createApplication('7');

Answer 1

How about defining an abstract class which gives you the PDO object on request?
E.g.
abstract class Db {
private static $x = null;
private static function init() {
try {
self::$x = new PDO(...);
} catch (PDOException $e) {
...
}
}
public static function getX() {
if (!self::$x) self::init();
return self::$x;
}
}

Answer 2

no need to have your class create an instance of itself if all you want is an instance of a different object back. maybe make a static method in Conn to return an instance of a db connection.
class Conn {
// prevent new statement
private __construct() {}
public static return_pdo() {
blah
blah
blah
return $db;
}
public static config($file) {
do stuff
}
}
then call statically
$pdo = Conn::return_pdo();

Answer 3

It's because new Conn() returns $Conn object, not the value from $Conn->Conn() method.
Try this:
class Conn{
function Conn() {
$db = new PDO($conf['dsn'], $conf['user'], $conf['pass']);
}
function get_db() {
return $this->db;
}
}
class Factory {
function createUser($id = NULL) {
$new_conn = new Conn();
$db = $new_conn->get_db();
}
}