header size

I created a child theme by making a child theme folder and uploading an altered style.css file for the twenty eleven theme.

Now, I’d like to change the height of the header. I looked up how to do this, and everybody says to make a functions.php file for your child theme and specify the header height there. When I upload a functions.php file to my twenty eleven child theme folder with:

<?php
define( ‘HEADER_IMAGE_WIDTH’, apply filters(
‘twentyeleven_header_image_width’, 1000 ) ),
define( ‘HEADER_IMAGE_HEIGHT’, apply_filters(
‘twentyeleven_header_image_height’, 600 ) );
?>

it causes my website (www.GrimmAles.com) to shut down.

In general, I’m just confused about how functions.php files are supposed to work alongside a style.css file. I’m a novice.

thanks