Question

In the past, I’ve always created a database class and in that class assigned a $connection attribute the connection via mysql_connect in a __construct method. In the same file, I would instantiate the class so that it was ready to go. Then whenever I needed that connection I would simply require that database file and add a global $connection in the method that need the $connection. What is the best way to achieve something similar or better using php’s PDO?

Answer 1

I believe that there’s no “Best” way to achieve what you ask but here is what I use. The function execute was designed according to my needs, you may change it however you want.

** EDIT **

By the way, I am using a singleton method in this class since I call the class several times from different files. Therefore, you may change that as well.

class DB
{
    /* Connection settings */
    private static $host = 'localhost';
    private static $user = 'root';
    private static $pass = 'your_pass';
    private static $base = 'your_db';

    private static $ins;   // pdo instance
    private static $class; // class object for singleton

    public static $counter; // counts how many times execute is called

    public function __construct()
    {

    }

    public static function connect($errMode = PDO::ERRMODE_SILENT)
    {
        if (!isset(self::$ins))
        {
            try 
            {
                self::$ins = new PDO("mysql:host=" . self::$host . ";" ."dbname=" . self::$base . ";", self::$user, self::$pass);
                self::$ins->setAttribute(PDO::ATTR_ERRMODE, $errMode);
                // PDO::ERRMODE_EXCEPTION
            }
            catch (Excpetion $ex) 
            {
                self::raiseError($ex);
            }
            $className = __CLASS__;
            self::$class = new $className;
        }
        return self::$class;
    }

    /**
     * Function to execute a given query
     * @param string $query : query string
     * @param string | array $param : parameter (either array of parameters or string)
     * @param bool $useBind : if true bindParam method will be used, else execute method will be called
     * @return PDOStatement
     */
    public function execute($query, $param, $useBind=true)
    {   
        self::$counter++;
        $stmt = self::$ins->prepare($query);

        if (!$useBind)
            $stmt->execute($param);
        else
        {
            if (is_array($param))
            {
                $size = sizeof($param);
                // if items within param param are array (e.g. array(array(value, name, type, length),
                //                                                   array(value, name, type, length))
                if ($size >= 1 && is_array($param[0]))
                {
                    $i = 1; // ? placeholder counter
                    foreach ($param as $arr)
                    {
                        $size = sizeof($arr);
                        if ($size == 1) // e.g. array('red')
                            $stmt->bindParam($i, $arr[0]);
                        else if ($size == 2) // e.g. array(':color', 'red')
                            $stmt->bindParam($arr[0], $arr[1]);
                        else if ($size == 3) // e.g. array(':color', 'red', PDO::PARAM_STR)
                            $stmt->bindParam($arr[0], $arr[1], $arr[2]);
                        else // e.g. array(':color', 'red', PDO::PARAM_STR, 12)
                            $stmt->bindParam($arr[0], $arr[1], $arr[2], $arr[3]);
                        $i++;
                    }
                }
                else if ($size == 1) // e.g. array(15)
                    $stmt->bindParam(1, $param[0]);
                else if ($size == 2) // e.g. array(':color', 'red')
                    $stmt->bindParam($param[0], $param[1]);
                else if ($size == 3) // e.g. array(':color', 'red', PDO::PARAM_STR)
                    $stmt->bindParam($param[0], $param[1], $param[2]);
                else if ($size == 4) // e.g. array(':color', 'red', PDO::PARAM_STR, 12)
                    $stmt->bindParam($param[0], $param[1], $param[2], $param[3]);
            }
            else // e.g. $db::execute($query, 15)
                $stmt->bindParam(1, $param);
            $stmt->execute();
        }

        return $stmt;
    }

    public function query($query)
    {
        self::$counter++;
        $result = self::$ins->query($query);
        return $result;
    }

    public function close()
    {
        self::$ins = null;
    }

    public function lastId()
    {
        $id = self::$ins->lastInsertId();
        return $id;
    }

    public function trans()
    {
        self::$ins->beginTransaction();
    }   

    public function commit()
    {
        self::$ins->commit();
    }

    public function rollBack()
    {
        self::$ins->rollBack();
    }

    private function raiseError($er)
    {
        throw new Exception($er);
    }

    public function counter()
    {
        return self::$counter;
    }
}