PHP OOP Database class using MySQLi and Singleton.

class.database.php

<?php
class DbConnector {
	private $_connection;
	private static $_instance; 
	private $_host = "host";
	private $_username = "username";
	private $_password = "password";
	private $_database = "dbname";
	private $_dbport   = 3306;
	
	public static function getInstance() {
		if(!self::$_instance) { 
			self::$_instance = new self();
		}
		return self::$_instance;
	}
	private function __construct() {
		$this->_connection = new mysqli($this->_host, $this->_username, 
			$this->_password, $this->_database, $this->_dbport);
		if(mysqli_connect_error()) {
			trigger_error("Fatal MySQL Connection Error " . mysql_connect_error(),
				 E_USER_ERROR);
		}
	}

	private function __clone() { }
	public function getConnection() {
		return $this->_connection;
	}
}

class SomeOtherClass
{
 $conn = DbConnector::getInstance();
 $db = $conn->getConnection();
	# use $db->*(*)......
}
?>