Using pdo query () and custom getValue () on the same database object?

class connector {
  private static $db;
  function __construct() {
    $this->db = null;
  private function connect() {
    $this->db = new PDO('mysql:host=localhost;dbname=database;charset=utf8','user','pass');
  public static function getDB() {
    if (!isset(self::$db)) {
      self::$db = new connector();
    return self::$db;


  // this was my original function, I had reduced it for less space. my deepest regrets, I won't do it again.
  public function getValue($sql,$val='') {
    if ($val != '') {
      $data = $this->db->prepare($sql);
      return $data->fetch(PDO::FETCH_COLUMN);
    else {
      return $this->db->query($sql)->fetch(PDO::FETCH_COLUMN);

using this class I can easily use the pdo database object from anywhere, with custom functions.

$db = connector::getDB();

// var_dump()
db:object(connector)#1 (1) {
  object(PDO)#2 (0) {

$db->getValue('SELECT foo FROM bar'); //succeeds

$db->query('SELECT foo FROM bar'));
// throws
// Fatal error:  Call to undefined method connector::query()

if I return the actual object param instead of the whole object:

return self::$db->db;
db:object(PDO)#2 (0) {

the queries exchange roles

$db->getValue('SELECT foo FROM bar');
// throws
// Fatal error:  Call to undefined method connector::getValue()

$db->query('SELECT foo FROM bar')); //succeeds

How can I have both with the same object, effectively using $db->query() and $db->getValue() in the same script.

First of all, your getValue() method lacks one essential feature - support for prepared statements. Without ability to run dynamical queries it's value is close to nothing.

Second, if you are using a singleton anyway - then there is no need for the extra method to get an instance - nowadays singleton can do it just by itself.

What about this one? I wrote it to make PDO usage less wordy, utilizing neat method chaining. DB static class is already a PDO instance, without the need to instantiate it with extra call. As a result, you can run any PDO command just anywhere:

DB::query('SELECT foo FROM bar LIMIT 1')->fetchColumn();

It takes little more space than yours but at least it is giving you access to full PDO syntax, including support for prepared statements

DB::prepare('SELECT foo FROM bar WHERE id=?')->execite([$id])->fetchColumn();

as well as all other fetch methods

DB::query('SELECT foo FROM bar')->fetchAll(PDO::FETCH_COLUMN);