Using PDO database class within other PHP classes - php

Question

I have a database class that uses PDO. Here's a portion example of it:
class db {
private $host;
private $username;
private $password;
private $con;
private $pdo;
public function __construct( $database = "dnname" )
{
$this->host = "localhost";
$this->username = "username";
$this->password = "pass";
$conStr = "host={$this->host};dbname={$database}";
try {
$this->pdo = new PDO( "mysql:$conStr", $this->username, $this->password );
$this->pdo->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
}
catch( PDOException $e ) {
echo "error ". $e->getMessage();
}
}
public function fetch_single_row($sql, $data)
{
if( $data !== null )
$data = array_values( $data ); // Incase it's an associative array
$sel = $this->pdo->prepare( $sql );
$sel->execute( $data );
$sel->setFetchMode( PDO::FETCH_OBJ );
$obj = $sel->fetch();
return $obj;
}
I would like to use this class and its functions (it has more than I've included) inside other classes.
I have tried many many different things, but the only thing that works so far is starting a new instance of db in every new class which I think is bad practice. For instance:
class cms {
function cms(){
$this->db = new db();
}
function is_admin($id) {
if($this->db->fetch_single_row("SELECT id FROM user WHERE id = ? LIMIT 1", array($id))){
return true;
} else {
return false;
}
}
in my index.php, I include these classes and use them:
include("db.class.php");
include("cms.class.php");
$cms = new cms();
if($cms->is_admin($id)){
//code here
}
What is the correct way to accomplish this?

Answer 1

Take a look into the Singleton Design Pattern, it works great for a DB class
I used to use a class like this for quite a while
abstract class DB
{
protected static $instance;
protected $db;
protected static $host = 'host';
protected static $user = 'user';
protected static $pass = 'pass';
protected static $database;
public static function getInstance()
{
if (!isset(self::$instance)) self::$instance = new static();
return self::$instance;
}
protected function __construct()
{
$this->db = new PDO(sprintf('mysql:host=%s;dbname=%s', static::$host, static::$database), static::$user, static::$pass);
$this->db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
public static function db()
{
return static::getInstance()->db;
}
public function fetch_single_row($sql, $data)
{
if( $data !== null )
$data = array_values( $data ); // Incase it's an associative array
$sel = self::db()->prepare( $sql );
$sel->execute( $data );
$sel->setFetchMode( PDO::FETCH_OBJ );
$obj = $sel->fetch();
return $obj;
}
}
I would then extend that class for each different database I would need to connect to
class Main extends DB
{
protected static $database = 'db';
}
You can then use the class like this
$db = Main::getInstance();
$obj = $db->fetch_single_row($sql, $data);