<?php
/**
 * DBConnection class
 * 
 * @author      Jordi Bassagañas
 * @copyright   2014 Jordi Bassagañas
 * @link        https://login.mql5.com/en/users/laplacianlab
 */
class DBConnection 
{ 
    /**
     * @var DBConnection Singleton instance
     */
    private static $instance;
    /**
     * @var mysqli Database handler
     */
    private $mysqli;
    /**
     *  Opens a new connection to the MySQL server
     */
    private function __construct()
    { 
        mysqli_report(MYSQLI_REPORT_STRICT);
        try {
            $this->mysqli = new MySQLI(DB_SERVER, DB_USER, DB_PASSWORD, DB_NAME); 
        } catch (Exception $e) {	
            throw new Exception('Unable to connect to the database, please, try again later.');
        }
    } 
    /**
     * Gets the singleton instance
     * @return type
     */
    public static function getInstance()
    {
        if (!self::$instance instanceof self) self::$instance = new self; 
        return self::$instance;
    } 
    /**
     * Gets the database handler
     * @return mysqli
     */
    public function getHandler()
    { 
        return $this->mysqli; 
    } 
    /**
     * Runs the given query
     * @param string $sql
     * @return mixed
     */
    public function query($sql)
    {
        $result = $this->mysqli->query($sql);
        if ($result === false)
        {	
            throw new Exception('Unable to run query, please, try again later.');
        }
        else
        {
            return $result;
        }
    } 
}