My first database connection

Question

I've bought a domain-hosting from a local company. Their customer service is pretty horrible.

My code for connecting to the database seems ok but still its not working. Here my code:

function __construct(){
    if(!@mysql_ping()){
        $this->db_connect();
    }
    $sql  = "SELECT value FROM settings WHERE field =  'auto_logout'";
    $res  = mysql_fetch_array($this->execute_single_query($sql));
    $this->LOGIN_DURATION = $res['value'];
}


private function db_connect(){
    // Mysql connect
    $link = @mysql_connect('localhost', 'created_who_has_all_prev', 'pass_note_my_cpanel_and_mysql_has_same_pass');

    if (!$link) {
        die('Could not connect: ' . mysql_error());
    }
    //echo 'Connected successfully<br/>';
    // Mysql select db select --->
    $db_selected = mysql_select_db($this->DB, $link);
    if (!$db_selected) {
        die ('Can\'t use specified Database : ' . mysql_error());
    }
    //echo "<br/>Database Selected<br/>";
    return $link;
}

And this is the snapshot:

Answer 1

Your main problem is that the link that you create isn't accessible. So, PHP tries to connect with defaults (apparently in your setup it means the user is root) and since it has no password, the connection fails which is the cause of most of your warning messages.

The last warning is a consequence of the others.

To fix this problem - as you haven't provided details of the actual parts that are executing the query - here is how to re-write your code so it works:

$mysqli = new mysqli("localhost", "user", "password", "database");
if ($mysqli->connect_errno) {
    echo "(".$mysqli->connect_errno.") ".$mysqli->connect_error;
}

$sql = "SELECT `value` FROM `settings` WHERE `field` = ?";
$stmt = $mysqli->prepare($sql);
$stmt->bind_param("s","auto_logout");

if (!$stmt->execute()) {
    echo "(".$stmt->errno.") ".$stmt->error;
}

$res = $stmt->get_result();
$row = $res->fetch_assoc();
LOGIN_DURATION = $row['field'];

Answer 2

This is really sloppy code. I would use PDO as it is secure. Below is a class you can use but study how it works and why it works.

class Core {

    public $dbh; // handle of the db connection
    private static $instance;

    private function __construct()  {

        $options = array(PDO::ATTR_PERSISTENT => true, PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION);

        $this->dbh = new PDO("mysql:host=localhost;dbname=dealership", "root", "",$options);            

    }

    public static function getInstance() {
        if (!self::$instance) {

        self::$instance = new self();

    }
    return self::$instance;
    }

    private function __clone() {}
    private function __wakeup() {}

}

In your code call it like below:

require "/classes/pdo.class.php";

 $db = Core::getInstance();

 $stmt = "SELECT `lastname` FROM `employees` where id = 2";

 $pep = $db->dbh->prepare($stmt);
 $pep->execute();


 foreach($pep->fetchAll(PDO::FETCH_ASSOC) as $row) {

     echo $row['lastname']. "\n";
  }

Make sure you look into PDO, prepared statments, and singleton pattern to understand why it works.