MySQL.

function db_connect()
{

    @$link = mysql_connect('localhost', 'db_user', 'dbpasswd');
    if (!$link) {
      die('db connection error')';
    }

    @$bool = mysql_select_db('db_name', $link);
    if (!$bool) {
      die('db not found')';
    }

    $query = "SET NAMES utf8";
    @$result = mysql_query($query);
    if (!$result) {
      die('db comunication failed');
    }

    return true;

}

$query = "SELECT `id`, `name`, `passwd`, `salt` FROM `users`  WHERE `name` = '$usr'";
@$result = mysql_query($query);
if (!$result) {
  die('db comunication failed')'
} else {
  if ($row = mysql_fetch_assoc($result)) {    // fetch associative array
    // yes we have result from DB, user is registered

    mysql_free_result($result); // free result set

    $salt = $row['salt'];
    $db_passwd = $row['passwd'];

  } else {
    user NOT in database
    die('unregistered user');
  }

}