How to combine multiple php/mysql database connections?

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?

Kolky · Accepted Answer · 2010-01-19 11:15:41Z

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);
  }
}

answered Jan 19, 2010 at 11:15

Kolky

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1 Comment

AndrewDFrazier Over a year ago

That does the trick. I was nearly there in my own attempts, but I'd forgotten to use global in front of the variables.

Franz · Accepted Answer · 2010-01-19 11:11:44Z

0

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

answered Jan 19, 2010 at 11:11

Franz

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1 Comment

AndrewDFrazier Over a year ago

That's what I normally do, but the file that has the creation of a class in it was where I couldn't get my already created connection to come into play. Thanks to Kolky's answer, though, it now works.

Silvio Donnini · Accepted Answer · 2010-01-19 11:17:50Z

0

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();
    }
    ...
}

answered Jan 19, 2010 at 11:17

Silvio Donnini

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AndrewDFrazier Over a year ago

I like the look of this but it I think I'd have to alter to many pages in my website that call my normal database connection. I'm going to look into it properly when I have more time, though, because I think I should be using more code like this and less of the basic stuff that I create.

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