PHP - PDO 'config' file equivalent

Question

This may be a question that has been answered before - if so please just leave a comment below and I'll remove this one.

I have been learning classes in PHP and at the same time making the jump to PDO.

One concept I cant seem to find is how to acomplish the equivalent to this with classes:

config.php

<?php

$host = 'localhost';
$user = 'user';
$pass = 'pass';

$con = mysql_connect($host, $user, $pass) or die("MySQL Error");
mysql_select_db("account_db", $con);

?>

another.php

<?php

require_once('config.php');

$selectStatement = "SELET foo FROM bar";
$selectQuery = mysql_query($selectStatement, $con);

?>

I haven't quite figured out how I would create a config file/class for a PDO connection and then use it in another class, i.e. Users as below:

<?php

class Users
{
    private $_userId;

    function setUserId($username)
    {
        // Use a predefined database handle to connect to a database to get the users ID - I assume using a preconfigured $dbh handle via an include or extend?
        $sth = $dbh->prepare("SELECT id FROM users WHERE username = :username");
        $sth->bindParam(':username', $username);
        ...
    }
}

?>

Thanks all :)

Answer 1

In my projects, I prefer using a class with a static member which holds the PDO object.

<?php
class DB
{
   private static $instance = null;
   public static function get()
   {
       if(self::$instance == null)
       {
           try
           {
               self::$instance = new PDO('mysql:host=localhost;dbname=name', 'user', 'abc123');
           } 
           catch(PDOException $e)
           {
               // Handle this properly
               throw $e;
           }
       }
       return self::$instance;
   }
}

The I can access it like so:

<?php
require 'DB.php';
class Users
{
    private $_userId;

    function setUserId($username)
    {
        // Using DB::get() to get the PDO object
        $sth = DB::get()->prepare("SELECT id FROM users WHERE username = :username");
        $sth->bindParam(':username', $username);
        ...
    }
}