Change the pakistani rupe symbol in WooCommerce only on checkout page

wc-change-pakistani-rupee-symbol.php

add_filter('woocommerce_currency_symbol', 'change_existing_currency_symbol', 10, 2);

function change_existing_currency_symbol( $currency_symbol, $currency ) {

	if ( ! is_checkout() ) {
		return $currency_symbol;
	}

    switch( $currency ) {
    	case 'PKR': $currency_symbol = 'PKR'; break;
    }

    return $currency_symbol;
}