Working with PDO object - MySQL

I am new to PDO and I have pretty simple 开发者_JAVA百科question. I have a simple function for connecting to DB:

function connectDB()
    {
        try {
            $dbh = new PDO('mysql:host='.Config::$db_server.';dbname='.Config::$db_name, Config::$db_login, Config::$db_password, array(
                PDO::ATTR_PERSISTENT => true
            ));
            $dbh->exec("SET CHARACTER SET utf8"); 
            $dbh = null;
        } catch (PDOException $e) {
            print "Error!: " . $e->getMessage() . "<br/>";
            die();
        }
    }

After calling this function I successfully connect to db. Later when trying to send a query using $dbh->query I got "Call to a member function query() on a non-object ". I do understand that - I don't have an instance of the class at the moment. But the only think to achieve that is to use $dbh = new PDO("settings") again, which is kind of stupid isn't? The function has no sense than. I tried to return the $dbh in the connectDB function (before the NULL statement) but it wasn't really working.

How should be this done properly?

It depends on your app's architecture, but I believe, you should make database handle a class variable, initialize it in constructor and use it later.

class DatabaseAccess{
    private $_db;
    public function __construct(){
        try {
            $this->_db = new PDO('mysql:host='.Config::$db_server.';dbname='.Config::$db_name, Config::$db_login, Config::$db_password, array(
                PDO::ATTR_PERSISTENT => true
            ));
            $this->_db->exec("SET CHARACTER SET utf8"); 
            //notice I removed "= null" part
        } catch (PDOException $e) {
            print "Error!: " . $e->getMessage() . "<br/>";
            die();
        }
    }

    public function getSomething(){
        //run your query here:
        return $this->_db->query('');
    }
}

You need to remove the $dbh = null; sentence in your function. With this sentence you are overwriting the connection with a null value, so anytime later you do $dbh->query(), it's like doing null->query(), and so that error appears.

Also, you need to save the handler, or it gets lost after your code exits that function. Add a return $dbh; at the end of your function or wrap it in a class.