class MyFactory implements GeoIO\Factory
{
    public function createPoint($dimension, array $coordinates, $srid = null)
    {
        return MyPoint($coordinates['x'], $coordinates['y']);
    }

    public function createLineString($dimension, array $points, $srid = null)
    {
        return MyLineString($points);
    }

    // ...
}

$factory = MyFactory();
$parser = new GeoIO\WKT\Parser\Parser($factory);

$myLineString = $parse->parse('LINESTRING(1 2, 2 2, 1 1)');