OOP QueryHandler in PHP

I have a simple database connection class which is using PDO:

/**
 * Class DatabaseConnection
 */
class DatabaseConnection implements Connection
{
    /**
     * @var null|PDO
     */
    private $instance = null;

    /**
     * @var string The host the Connection should connect to
     */
    private $host;

    /**
     * @var string The database name the connection should connect to
     */
    private $database;

    /**
     * @var string The username to login into the database
     */
    private $username;

    /**
     * @var string The password to login into the database
     */
    private $password;

    /**
     * @var array The credentials from the database connection
     */
    private $credentials = [];

    /**
     * @var array The flags from the database connection
     */
    private $flags = [];

    /**
     * @param float  $host
     * @param string $database
     * @param string $username
     * @param string $password
     * @param array  $credentials
     * @param array  $flags
     */
    public final function __construct($host, $database, $username, $password, $credentials = [], $flags = []) {
        $this->host        = $host;
        $this->database    = $database;
        $this->username    = $username;
        $this->password    = $password;
        $this->credentials = $credentials;
        $this->flags       = $flags;
    }

    /**
     * @throws ConnectionException
     */
    public final function initialize() {
        if ($this->isInitialized()) {
            throw new ConnectionException("Database connection isnt open yet.");
        }
        $this->instance = new PDO("mysql:host=$this->host;dbname=$this->database", $this->username, $this->password);
    }

    /**
     * Closes the connection
     *
     * @throws ConnectionException When the connection isn't open
     */
    public final function terminate() {
        if (!$this->isInitialized()) {
            throw new ConnectionException("Database is closed");
        }
        $this->instance = null;
    }

    /**
     * @return bool
     */
    private function isInitialized() {
        return $this->instance !== null;
    }

    /**
     * @param $credentials
     */
    public final function setCredentials($credentials) {
        $this->credentials = $credentials;
    }

    /**
     * @return null|PDO
     */
    public function getInstance() {
        return $this->instance;
    }
}

For queries, i've made this class:

/**
 * User: Bas
 * Date: 8-12-2014
 * Time: 10:36
 */
class QueryHandler
{

    /**
     * @var DatabaseConnection $databaseConnection
     */
    private $databaseConnection;

    /**
     * @var PDOStatement The query which is getting executed
     */
    private $statement;

    /**
     * Initializes the variable for the current database connection where the query should run on
     *
     * @param DatabaseConnection $databaseConnection The database connection
     */
    public final function __construct (DatabaseConnection $databaseConnection) {
        $this->databaseConnection = $databaseConnection;
    }

    /**
     * Prepares the query and gives the opportunity to already give the parameters
     *
     * @param PDOStatement $statement  The query which is getting executed.
     * @param array        $parameters The parameters contained in the query
     *
     * @return $this This class, used for method chaining
     */
    public final function build ($statement, array $parameters = []) {
        /*
         * Prepare the query
         */
        $this->statement = $this->databaseConnection->getInstance()
                                                    ->prepare($statement);
        /*
         * Check if there are any parameter in the query
         */
        if (preg_match_all('/(?<=:)\w+/', $statement, $parameter) && !empty($parameters)) {
            /*
             * Loop through the parameter names and values
             */
            foreach ($parameters as $parameter => $value) {
                /*
                 * Bind the parameters within the query
                 */
                $this->statement->bindParam($parameter, $value);
            }
        } elseif (!empty($parameters) && !preg_match_all('/(?<=:)\w+/', $statement, $parameter)) {
            unset($parameters);
        }
        /*
         * Return the class used for method chaining
         */
        return $this;
    }

    /**
     * Executes the given query
     *
     * @return $this Executes the given query
     */
    public final function execute () {
        $this->statement->execute();

        return $this;
    }

    /**
     * Fetch a single row out of the database based on the query
     *
     * @param int $fetchStyle
     *
     * @return int|string|float|array
     */
    public final function getResult ($fetchStyle = PDO::FETCH_ASSOC) {
        return $this->statement->fetch($fetchStyle);
    }

    /**
     * Fetches multiple row
     *
     * @param int $fetchStyle
     *
     * @return int|string|float|array
     */
    public final function getResults ($fetchStyle = PDO::FETCH_ASSOC) {
        return $this->statement->fetchAll($fetchStyle);
    }

    /**
     * Sets the parameters of the given query
     *
     * @param array $parameters
     *
     * @return $this
     */
    public function setParameters (array $parameters) {
        foreach ($parameters as $parameter => $value) {
            $this->statement->bindParam(":" . $parameter, $value);
        }
        return $this;
    }
}

To use this, i use this code:

$connection = new DatabaseConnection("127.0.0.1", "phpmyadmin", "root", "", array());

try {
    $connection->initialize();

    $queryHandler = new QueryHandler($connection);

    $result = $queryHandler->build("SELECT table_name, column_name, comment FROM pma_column_info")
                           ->execute()
                           ->getResult();


} catch (ConnectionException $e) {
     ....
}

This is only for getinng a value out of the database, for inserting something into the database i can just do:

$queryHandler->build("INSERT INTO ....")->execute();

Note

• This is for practice