Redirect to checkout after click add to cart

functions.php

<?php
// redirect to checkout after click 'add to cart'  - Woocommerce
add_filter ('add_to_cart_redirect', 'redirect_to_checkout');

function redirect_to_checkout() {
    global $woocommerce;
    $checkout_url = $woocommerce->cart->get_checkout_url();
    return $checkout_url;
}


// redirect checkout to shop when cart is empty

    add_action( 'template_redirect', function() {
        if ( ! is_cart() ) { return; }
        if ( WC()->cart->get_cart_contents_count() == 0 ) {
            wp_redirect( apply_filters( 'wmsc_redirect', wc_get_page_permalink( 'shop' ) ) );
            exit;
        }

        // Redirect to checkout page
        wp_redirect( wc_get_checkout_url(), '301' );
        exit;
    } );

    add_action('template_redirect', 'redirection_function');

    function redirection_function(){
        global $woocommerce;

        if( is_checkout() && 0 == sprintf(_n('%d', '%d', $woocommerce->cart->cart_contents_count, 'woothemes'), $woocommerce->cart->cart_contents_count) && !isset($_GET['key']) ) {
            wp_redirect( apply_filters( 'wmsc_redirect', wc_get_page_permalink( 'shop' ) ) );
            exit;
        }
    }