How To Use PDO to connect to mysql

<?php
class connect{
         public $db_host= "localhost"; //database host e.g. localhost,127.0.0.1
         public $username="admin";     //username of sql server
         public $password= "pass";     //password of sql server
         public $db_name="dbtest";     //name of existing database on server

         private $dbc=null;  //database identifier

    function __construct(){
        try{
            $this->dbc= new PDO("mysql:host=$this->db_host; dbname=$this->db_name", $this->username, $this->password);
        }
        catch (PDOException $e){
            $this->dbc=null;
            echo 'Connection failed: ' . $e->getMessage();
            exit();
           }
    }

    /*
     * To run this tester, make sure your database contains a table called users with a field called email with at least one value
     *
     */
     public function tester2(){
         $result = $this->dbc->query("SELECT * FROM `users` ", PDO::FETCH_ASSOC);
         foreach($result as $row) {
                var_dump($row);
         }
    }

    /*
     * You do not need any table to test this one
     */
    public function tester(){
        $result = $this->dbc->query("SELECT 1+1 FROM `users` ", PDO::FETCH_ASSOC);
        foreach($result as $row) {
            var_dump($row);
        }
    }
}

$connection = new connect();

$connection->tester();

$connection->tester2();

?>