Group shipping rates

functions.php

add_filter('woocommerce_package_rates', 'wf_group_rates', 10, 2);
	
function wf_group_rates($rates, $package){
	$groups	=	array(
		array(
			'group_name'=>	'Mail Express',
			'ids'		=>	array('wf_shipping_usps:D_EXPRESS_MAIL','wf_shipping_usps:flat_rate_box_express'),
			'operator'	=>	'min',
		),
		array(
			'group_name'=>	'Standard Mail',
			'ids'		=>	array('wf_shipping_usps:D_FIRST_CLASS','wf_shipping_usps:D_STANDARD_POST'),
			'operator'	=>	'min',
		),
	);
	
	// Divide rates into groups
	foreach($groups as $group_key => $group){
		$groups[$group_key]['rates']	=	array();
		
		foreach($rates as $rate_key => $rate){
			if(in_array($rate->id, $group['ids'])){
				$groups[$group_key]['rates'][]	=	$rate;
				unset($rates[$rate_key]);
			}
		}
	}
	
	
	foreach($groups as $group_key => $group){
		if(is_array($group['rates']) && count($group['rates'])){
			//Get lowest/highest rate and assign back with group name
			$selected_rate			=	current(wf_sort_rate_by_cost($group['rates'], $group['operator']));
			$selected_rate->label	=	$group['group_name'];
			$rates[$selected_rate->id]	=	$selected_rate;
		}
	}
	return $rates;
}

function wf_sort_rate_by_cost($rates, $op = 'min'){
	usort($rates, function($rate1, $rate2) use ($op){
		if($rate1->cost == $rate2->cost){
			return 0;
		}
		switch($op){
			case 'min':default:
				return ($rate1->cost < $rate2->cost) ? -1 : 1;
				
			case 'max':
				return ($rate1->cost > $rate2->cost) ? -1 : 1;
		}
	});
	return $rates;
}