How to combine multiple php/mysql database connections? - php

Question

When building dynamic websites I use a php include to make my connections to the database. The included file is very basic:
mysql_connect($hostname = 'host', $username = 'user', $password = 'password');
mysql_select_db('database');
This works fine.
In some places I use an AJAX system to create drag-and-drop reordering of database records which updates the database at the same time, it is adapted from something I found on the internet. This uses its own connection code:
class SortableExample {
protected $conn;
protected $user = 'user';
protected $pass = 'password';
protected $dbname = 'database';
protected $host = 'host';
public function __construct() {
$this->conn = mysql_connect($this->host, $this->user, $this->pass);
mysql_select_db($this->dbname,$this->conn);
}
This also woks fine.
What it means, however, is that I have to add the username, password, host and database to two separate files. Sometimes the second one is forgotten and causes the website to fail.
My question is, how can I either combine both connection files into one, OR how can I get the second block of code to accept external variables so that I only have to enter the actual values in one place?

Answer 1

Your last question is easy.
db.config.php
$host = '';
$user = '';
$pass = '';
$db = '';
db.plain.php
include 'db.config.php';
$conn = mysql_connect($host, $user, $pass);
mysql_select_db($db,$conn);
db.class.php
include 'db.config.php';
class SortableExample
{
protected $conn;
public function __construct()
{
global $host, $user, $pass, $db;
$this->conn = mysql_connect($host, $user, $pass);
mysql_select_db($db,$this->conn);
}
}

Answer 2

You can simply put the database connection code in another file and included that everywhere you need it.

Answer 3

Create a single entry point for your database connection.
Use a Singleton with lazy instantiation for that:
class ConnectionProvider {
protected $conn;
protected $user = 'user';
protected $pass = 'password';
protected $dbname = 'database';
protected $host = 'host';
private static $__instance;
private function __construct() {
$this->conn = mysql_connect($this->host, $this->user, $this->pass);
mysql_select_db($this->dbname,$this->conn);
}
public static function getInstance() {
if ( self::$__instance == null) {
self::$__instance = new ConnectionProvider();
}
return self::$__instance;
}
public function getConnection() {
return $this->conn;
}
}
And then, from your code
ConnectionProvider::getInstance()->getConnection();
to use the connection wherever you need it.
SortableExample would thus become:
class SortableExample {
protected $conn;
public function __construct() {
$this->conn = ConnectionProvider::getInstance()->getConnection();
}
...
}