PDO connection

<?php
  $nameserver = $_SERVER['HTTP_HOST'];
  $servername = NULL;
  $username = NULL;
  $password = NULL;
  $mydb = NULL;
  if(strpos($nameserver,"localhost") !== false){
    //nous somme en localhost
    $servername = "localhost";
    $username = "root";
    $password = "";
    $mydb = "####";
  }else{
    //nous somme en ligne
    $servername = "";
    $username = "";
    $password = "";
    $mydb = "";
  }

  try {
    $conn = new PDO("mysql:host=$servername;dbname=$mydb;charset=utf8",$username,$password);
    //cette commande permet d'afficher les erreurs
    $conn->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
     //echo "CONNECTION REUSSI";
  } catch (PDOException $e) {
    echo "CONNECTION ECHOUER :".$e->getMessage();
  }