PDO wont connect to the database - php

Question

I've made a simple Database class to handle my database connections. But it's somehow not working? At first it wasn't working with MySQLi, so i tried PDO – which ain't working either.
I am however eager to make PDO work. I've already googled and searched here at StackOverflow, but without luck.
Here's my class:
class Database
{
// Local
protected $_host = "localhost";
protected $_user = "root";
protected $_pass = "root";
protected $_database = "hs";
protected $_connection;
// Construct
private function __construct()
{
try
{
$this->_connection = new PDO('mysql:host=localhost;dbname=hs', $this->_user, $this->_pass);
$this->_connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $e)
{
echo 'ERROR: ' . $e->getMessage();
}
}
public function login($usr, $pwd)
{
echo "hi";
}
}
And here's the execution:
if(isset($_POST['hs_login']))
{
$db = new Database;
$db->login($_POST['hs_username'], $_POST['hs_password']);
}
Thanks in advance! :)

Answer 1

Constructors are always public so change that like so:
class Database
{
// Local
protected $_host = "localhost";
protected $_user = "root";
protected $_pass = "root";
protected $_database = "hs";
protected $_connection;
// Construct
public function __construct()
{
try
{
$this->_connection = new PDO('mysql:host=localhost;dbname=hs', $this->_user, $this->_pass);
$this->_connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $e)
{
echo 'ERROR: ' . $e->getMessage();
}
}
public function login($usr, $pwd)
{
echo "hi";
}
}
Also, new Database is a method call so change that like so:
if(isset($_POST['hs_login']))
{
$db = new Database;
$db->login($_POST['hs_username'], $_POST['hs_password']);
}

Answer 2

Just wanted to point out, that there are some cases, when you can use private constructors. One of the practical use of them is with Databases, so it's relevant in your case as well. This design pattern is called Singleton pattern, and it relies on static method calls. You don't have to instantiate the class, as instantiation is handled by the class itself. I've put together an example:
<?php
class Database {
private static $instance = null;
private $db;
private static $last_result;
private function __construct() {
try {
$pdo_param = array(
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC
);
$this->db = new PDO("mysql:host=YOUR_HOSTNAME;dbname=YOUR_DBNAME", "YOUR_USERNAME", "YOUR_PASSWORD", $pdo_param);
}
catch (PDOException $e) {
die($e->getMessage());
}
}
private static function getInstance() {
if (self::$instance == null) {
self::$instance = new self();
}
return self::$instance;
}
public static function query($sql) {
try {
$instance = self::getInstance();
$stmt = $instance->db->prepare($sql);
$stmt->execute();
self::$last_result = $stmt->fetchAll();
return self::$last_result;
}
catch (PDOException $e) {
die($e->getMessage());
}
}
public static function prepare($sql, $params) {
try {
$instance = self::getInstance();
$stmt = $instance->db->prepare($sql);
$stmt->execute($params);
self::$last_result = $stmt->fetchAll();
return self::$last_result;
}
catch (PDOException $e) {
die($e->getMessage());
}
}
}
$users = Database::query("SELECT * FROM users");
$filtered_users = Database::prepare("SELECT * FROM users WHERE username = :username", array(":username" => "john_doe"));
?>
<pre><?php
print_r($users);
print_r($filtered_users);
?></pre>
Singleton design pattern is really useful when you want to make sure, that there's ONLY ONE instance of a class in any given time.