php code for weight based shipping plug in

Hi there, I hope someone here can help. I posted this elsewhere, but it seems more appropriate to post it here.

I need to be able exclude a group of products from weight based shipping in favour of flat rate, but still keep weight based shipping as the main/default shipping system.

I’ve been using a reworked version of the ‘hide other shipping methods’ code, but so far it has only returned an error:

call_user_func_array() expects parameter 1 to be a valid callback, function ‘hide_standard_shipping_when_free_is_available’ not found or invalid function name in /home/poppyl5/public_html/wp-includes/plugin.php on line 173

Basically I exchanged ‘free shipping’ for ‘flat rate’ but it doesn’t to be quite that simple.

function hide_all_shipping_when_flat_rate_is_available( $available_methods ) {

  	if( isset( $available_methods['flat_rate'] ) ) :

		// Get Flat Rate array into a new array
		$flatrate = array();
		$flatrate = $available_methods['flat_rate'];

		// Empty the $available_methods array
		unset( $available_methods );

		// Add Flat Rate back into $avaialble_methods
		$available_methods = array();
		$available_methods[] = $flatrate;

	endif;

	return $available_methods;
}

I’m just starting out with php, so if you have an answer, please make it easily understandable for a beginner. It would be great if you could give an explanation too, so I can go away, think it through and add another level of understanding to my programming.

Thankyou in advance 🙂

The site I’m working on is based around Woocommerce and Wootique.

If you need anything making clearer, just ask.