WooCommerce cart: Change shipping rate based on contents count and another example based on total purchased.

functions.php

// Change shipping based on quantity purchased.
// https://easywebdesigntutorials.com/adjust-shipping-price-when-quantity-changes/
// https://businessbloomer.com/woocommerce-setup-tiered-shipping-rates-order-amount/
add_filter( 'woocommerce_package_rates', 'bbloomer_woocommerce_tiered_shipping', 10, 2 );
function bbloomer_woocommerce_tiered_shipping( $rates, $package ) {
    $threshold1 = 2; 
    $threshold2 = 3;
      if ( WC()->cart->get_cart_contents_count() < $threshold1 ) {
       unset( $rates['flat_rate:6'], $rates['flat_rate:8']  );
    } elseif ( WC()->cart->get_cart_contents_count() < $threshold2 ){
        unset( $rates['flat_rate:1'], $rates['flat_rate:8'] ); 
	} else {
        unset( $rates['flat_rate:1'], $rates['flat_rate:6'] );
    }  
    return $rates;  
}
                                                                  
                                                                  
/* Change shipping based on total cost purchased. */
add_filter( 'woocommerce_package_rates', 'bbloomer_woocommerce_tiered_shipping', 10, 2 );
function bbloomer_woocommerce_tiered_shipping( $rates, $package ) {
$threshold1 = 2000; 
$threshold2 = 4000;
   if ( WC()->cart-> cart_contents_total < $threshold1 ) {
     unset( $rates['flat_rate:9'], $rates['flat_rate:10'] );
 } elseif ( WC()->cart-> cart_contents_total < $threshold2 ) {
     unset( $rates['flat_rate:8'], $rates['flat_rate:10'] ); 
 } else {
     unset( $rates['flat_rate:8'], $rates['flat_rate:9'] );
} 
return $rates; 
}