<?php
class Database{
private $hostdb = "localhost";
private $namedb = "bd_name";
private $userdb = "root";
private $passdb = "";
public $pdo;

public function __construct(){
if(!isset($this->pdo)){
try{
$link = new PDO("mysql:host=".$this->hostdb.";dbname=".$this->namedb, $this->userdb, $this->passdb);
$link->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$link->exec("SET CHARACTER SET utf8");
$this->pdo = $link;
}
catch (PDOException $rex){
die("Failed to connect with database".$rex->getMessage());
}
}
}
}
?>
**********************************************
Using OOP const(constant)
**********************************************
<?php
class Database {
const HOST = "localhost";
const USER = "root";
const PASS = "";
const DB   = "bd_name";
public $conn;

public function __construct(){
if (!isset($this->conn)) {
try {
$sql = new PDO("mysql:host=" . Database::HOST . ";dbname=" . Database::DB, Database::USER, Database::PASS);
$sql->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$sql->exec("SET CHARACTER SET utf8");
$this->conn = $sql;
} catch (PDOException $e) {
die("Faied to connection with Database!".$e->getMessage());
}
}
}
}
?>