/**
 * Hide shipping rates when free shipping is available.
 * Updated to support WooCommerce 2.6 Shipping Zones.
 *
 * @param array $rates Array of rates found for the package.
 * @return array
 */
function my_hide_shipping_when_free_is_available( $rates ) {
	$free = array();
	foreach ( $rates as $rate_id => $rate ) {
		if ( 'free_shipping' === $rate->method_id ) {
			$free[ $rate_id ] = $rate;
			break;
		}
	}
	return ! empty( $free ) ? $free : $rates;
}
add_filter( 'woocommerce_package_rates', 'my_hide_shipping_when_free_is_available', 100 );

/**
 * Hide shipping rates when free shipping is available, but keep "Local pickup" 
 * Updated to support WooCommerce 2.6 Shipping Zones
 */

function hide_shipping_when_free_is_available( $rates, $package ) {
	$new_rates = array();
	foreach ( $rates as $rate_id => $rate ) {
		// Only modify rates if free_shipping is present.
		if ( 'free_shipping' === $rate->method_id ) {
			$new_rates[ $rate_id ] = $rate;
			break;
		}
	}

	if ( ! empty( $new_rates ) ) {
		//Save local pickup if it's present.
		foreach ( $rates as $rate_id => $rate ) {
			if ('local_pickup' === $rate->method_id ) {
				$new_rates[ $rate_id ] = $rate;
				break;
			}
		}
		return $new_rates;
	}

	return $rates;
}

add_filter( 'woocommerce_package_rates', 'hide_shipping_when_free_is_available', 10, 2 );

/**
 * Hide ALL shipping options when free shipping is available and customer is NOT in certain states
 *
 * Change $excluded_states = array( 'AK','HI','GU','PR' ); to include all the states that DO NOT have free shipping
 */
add_filter( 'woocommerce_package_rates', 'hide_all_shipping_when_free_is_available' , 10, 2 );

/**
 * Hide ALL Shipping option when free shipping is available
 *
 * @param array $available_methods
 */
function hide_all_shipping_when_free_is_available( $rates, $package ) {
 
	$excluded_states = array( 'AK','HI','GU','PR' );
	if( isset( $rates['free_shipping'] ) AND !in_array( WC()->customer->shipping_state, $excluded_states ) ) :
		// Get Free Shipping array into a new array
		$freeshipping = array();
		$freeshipping = $rates['free_shipping'];
 
		// Empty the $available_methods array
		unset( $rates );
 
		// Add Free Shipping back into $avaialble_methods
		$rates = array();
		$rates[] = $freeshipping;
 
	endif;
 
	if( isset( $rates['free_shipping'] ) AND in_array( WC()->customer->shipping_state, $excluded_states ) ) {
 
		// remove free shipping option
		unset( $rates['free_shipping'] );
 
	}

	return $rates;
}