<form method="POST">
    <h3>Editing: class-wc-shortcode-checkout.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php
/**
 * Checkout Shortcode
 *
 * Used on the checkout page, the checkout shortcode displays the checkout process.
 *
 * @package WooCommerce\Shortcodes\Checkout
 * @version 2.0.0
 */

defined( 'ABSPATH' ) || exit;

use Automattic\WooCommerce\Internal\Utilities\Users;

/**
 * Shortcode checkout class.
 */
class WC_Shortcode_Checkout {

	/**
	 * Get the shortcode content.
	 *
	 * @param array $atts Shortcode attributes.
	 * @return string
	 */
	public static function get( $atts ) {
		return WC_Shortcodes::shortcode_wrapper( array( __CLASS__, 'output' ), $atts );
	}

	/**
	 * Output the shortcode.
	 *
	 * @param array $atts Shortcode attributes.
	 */
	public static function output( $atts ) {
		global $wp;

		// Check cart class is loaded or abort.
		if ( is_null( WC()-&gt;cart ) ) {
			return;
		}

		// Backwards compatibility with old pay and thanks link arguments.
		if ( isset( $_GET['order'] ) &amp;&amp; isset( $_GET['key'] ) ) { // WPCS: input var ok, CSRF ok.
			wc_deprecated_argument( __CLASS__ . '-&gt;' . __FUNCTION__, '2.1', '&quot;order&quot; is no longer used to pass an order ID. Use the order-pay or order-received endpoint instead.' );

			// Get the order to work out what we are showing.
			$order_id = absint( $_GET['order'] ); // WPCS: input var ok.
			$order    = wc_get_order( $order_id );

			if ( $order &amp;&amp; $order-&gt;has_status( 'pending' ) ) {
				$wp-&gt;query_vars['order-pay'] = absint( $_GET['order'] ); // WPCS: input var ok.
			} else {
				$wp-&gt;query_vars['order-received'] = absint( $_GET['order'] ); // WPCS: input var ok.
			}
		}

		// Handle checkout actions.
		if ( ! empty( $wp-&gt;query_vars['order-pay'] ) ) {

			self::order_pay( $wp-&gt;query_vars['order-pay'] );

		} elseif ( isset( $wp-&gt;query_vars['order-received'] ) ) {

			self::order_received( $wp-&gt;query_vars['order-received'] );

		} else {

			self::checkout();

		}
	}

	/**
	 * Show the pay page.
	 *
	 * @throws Exception When validate fails.
	 * @param int $order_id Order ID.
	 */
	private static function order_pay( $order_id ) {

		do_action( 'before_woocommerce_pay' );

		$order_id = absint( $order_id );

		// Pay for existing order.
		if ( isset( $_GET['pay_for_order'], $_GET['key'] ) &amp;&amp; $order_id ) { // WPCS: input var ok, CSRF ok.
			try {
				$order_key = isset( $_GET['key'] ) ? wc_clean( wp_unslash( $_GET['key'] ) ) : ''; // WPCS: input var ok, CSRF ok.
				$order     = wc_get_order( $order_id );

				// Order or payment link is invalid.
				if ( ! $order || $order-&gt;get_id() !== $order_id || ! hash_equals( $order-&gt;get_order_key(), $order_key ) ) {
					throw new Exception( __( 'Sorry, this order is invalid and cannot be paid for.', 'woocommerce' ) );
				}

				// Logged out customer does not have permission to pay for this order.
				if ( ! current_user_can( 'pay_for_order', $order_id ) &amp;&amp; ! is_user_logged_in() ) {
					wc_print_notice( esc_html__( 'Please log in to your account below to continue to the payment form.', 'woocommerce' ), 'notice' );
					woocommerce_login_form(
						array(
							'redirect' =&gt; $order-&gt;get_checkout_payment_url(),
						)
					);
					return;
				}

				// Add notice if logged in customer is trying to pay for guest order.
				if ( ! $order-&gt;get_user_id() &amp;&amp; is_user_logged_in() ) {
					// If order has does not have same billing email then current logged in user then show warning.
					if ( $order-&gt;get_billing_email() !== wp_get_current_user()-&gt;user_email ) {
						wc_print_notice( __( 'You are paying for a guest order. Please continue with payment only if you recognize this order.', 'woocommerce' ), 'error' );
					}
				}

				// Logged in customer trying to pay for someone else's order.
				if ( ! current_user_can( 'pay_for_order', $order_id ) ) {
					throw new Exception( __( 'This order cannot be paid for. Please contact us if you need assistance.', 'woocommerce' ) );
				}

				// Does not need payment.
				if ( ! $order-&gt;needs_payment() ) {
					/* translators: %s: order status */
					throw new Exception( sprintf( __( 'This order&amp;rsquo;s status is &amp;ldquo;%s&amp;rdquo;&amp;mdash;it cannot be paid for. Please contact us if you need assistance.', 'woocommerce' ), wc_get_order_status_name( $order-&gt;get_status() ) ) );
				}

				// Ensure order items are still stocked if paying for a failed order. Pending orders do not need this check because stock is held.
				if ( ! $order-&gt;has_status( wc_get_is_pending_statuses() ) ) {
					$quantities = array();

					foreach ( $order-&gt;get_items() as $item_key =&gt; $item ) {
						if ( $item &amp;&amp; is_callable( array( $item, 'get_product' ) ) ) {
							$product = $item-&gt;get_product();

							if ( ! $product ) {
								continue;
							}

							$quantities[ $product-&gt;get_stock_managed_by_id() ] = isset( $quantities[ $product-&gt;get_stock_managed_by_id() ] ) ? $quantities[ $product-&gt;get_stock_managed_by_id() ] + $item-&gt;get_quantity() : $item-&gt;get_quantity();
						}
					}

					// Stock levels may already have been adjusted for this order (in which case we don't need to worry about checking for low stock).
					if ( ! $order-&gt;get_data_store()-&gt;get_stock_reduced( $order-&gt;get_id() ) ) {
						foreach ( $order-&gt;get_items() as $item_key =&gt; $item ) {
							if ( $item &amp;&amp; is_callable( array( $item, 'get_product' ) ) ) {
								$product = $item-&gt;get_product();

								if ( ! $product ) {
									continue;
								}

								if ( ! apply_filters( 'woocommerce_pay_order_product_in_stock', $product-&gt;is_in_stock(), $product, $order ) ) {
									/* translators: %s: product name */
									throw new Exception( sprintf( __( 'Sorry, &quot;%s&quot; is no longer in stock so this order cannot be paid for. We apologize for any inconvenience caused.', 'woocommerce' ), $product-&gt;get_name() ) );
								}

								// We only need to check products managing stock, with a limited stock qty.
								if ( ! $product-&gt;managing_stock() || $product-&gt;backorders_allowed()  ) {
									continue;
								}

								// Check stock based on all items in the cart and consider any held stock within pending orders.
								$held_stock     = wc_get_held_stock_quantity( $product, $order-&gt;get_id() );
								$required_stock = $quantities[ $product-&gt;get_stock_managed_by_id() ];

								if ( ! apply_filters( 'woocommerce_pay_order_product_has_enough_stock', ( $product-&gt;get_stock_quantity() &gt;= ( $held_stock + $required_stock ) ), $product, $order ) ) {
									/* translators: 1: product name 2: quantity in stock */
									throw new Exception( sprintf( __( 'Sorry, we do not have enough &quot;%1$s&quot; in stock to fulfill your order (%2$s available). We apologize for any inconvenience caused.', 'woocommerce' ), $product-&gt;get_name(), wc_format_stock_quantity_for_display( $product-&gt;get_stock_quantity() - $held_stock, $product ) ) );
								}
							}
						}
					}
				}

				// If we cannot match the order with the current user, ask that they verify their email address.
				if ( self::guest_should_verify_email( $order, 'order-pay' ) ) {
					wc_get_template(
						'checkout/form-verify-email.php',
						array(
							'failed_submission' =&gt; ! empty( $_POST['email'] ), // phpcs:ignore WordPress.Security.NonceVerification.Missing
							'verify_url'        =&gt; $order-&gt;get_checkout_payment_url(),
						)
					);
					return;
				}

				WC()-&gt;customer-&gt;set_props(
					array(
						'billing_country'  =&gt; $order-&gt;get_billing_country() ? $order-&gt;get_billing_country() : null,
						'billing_state'    =&gt; $order-&gt;get_billing_state() ? $order-&gt;get_billing_state() : null,
						'billing_postcode' =&gt; $order-&gt;get_billing_postcode() ? $order-&gt;get_billing_postcode() : null,
					)
				);
				WC()-&gt;customer-&gt;save();

				$available_gateways = WC()-&gt;payment_gateways-&gt;get_available_payment_gateways();

				if ( count( $available_gateways ) ) {
					current( $available_gateways )-&gt;set_current();
				}

				/**
				 * Allows the text of the submit button on the Pay for Order page to be changed.
				 *
				 * @param string $text The text of the button.
				 *
				 * @since 3.0.2
				 */
				$order_button_text = apply_filters( 'woocommerce_pay_order_button_text', __( 'Pay for order', 'woocommerce' ) );

				/**
				 * Triggered right before the Pay for Order form, after validation of the order and customer.
				 *
				 * @param WC_Order $order              The order that is being paid for.
				 * @param string   $order_button_text  The text for the submit button.
				 * @param array    $available_gateways All available gateways.
				 *
				 * @since 6.6
				 */
				do_action( 'before_woocommerce_pay_form', $order, $order_button_text, $available_gateways );

				wc_get_template(
					'checkout/form-pay.php',
					array(
						'order'              =&gt; $order,
						'available_gateways' =&gt; $available_gateways,
						'order_button_text'  =&gt; $order_button_text,
					)
				);

			} catch ( Exception $e ) {
				wc_print_notice( $e-&gt;getMessage(), 'error' );
			}
		} elseif ( $order_id ) {

			// Pay for order after checkout step.
			$order_key = isset( $_GET['key'] ) ? wc_clean( wp_unslash( $_GET['key'] ) ) : ''; // WPCS: input var ok, CSRF ok.
			$order     = wc_get_order( $order_id );

			if ( $order &amp;&amp; $order-&gt;get_id() === $order_id &amp;&amp; hash_equals( $order-&gt;get_order_key(), $order_key ) ) {

				if ( $order-&gt;needs_payment() ) {

					wc_get_template( 'checkout/order-receipt.php', array( 'order' =&gt; $order ) );

				} else {
					/* translators: %s: order status */
					wc_print_notice( sprintf( __( 'This order&amp;rsquo;s status is &amp;ldquo;%s&amp;rdquo;&amp;mdash;it cannot be paid for. Please contact us if you need assistance.', 'woocommerce' ), wc_get_order_status_name( $order-&gt;get_status() ) ), 'error' );
				}
			} else {
				wc_print_notice( __( 'Sorry, this order is invalid and cannot be paid for.', 'woocommerce' ), 'error' );
			}
		} else {
			wc_print_notice( __( 'Invalid order.', 'woocommerce' ), 'error' );
		}

		do_action( 'after_woocommerce_pay' );
	}

	/**
	 * Show the thanks page.
	 *
	 * @param int $order_id Order ID.
	 */
	private static function order_received( $order_id = 0 ) {
		$order = false;

		// Get the order.
		$order_id  = apply_filters( 'woocommerce_thankyou_order_id', absint( $order_id ) );
		$order_key = apply_filters( 'woocommerce_thankyou_order_key', empty( $_GET['key'] ) ? '' : wc_clean( wp_unslash( $_GET['key'] ) ) ); // WPCS: input var ok, CSRF ok.

		if ( $order_id &gt; 0 ) {
			$order = wc_get_order( $order_id );

			if ( ( ! $order instanceof WC_Order ) || ! hash_equals( $order-&gt;get_order_key(), $order_key ) ) {
				$order = false;
			}
		}

		// Empty awaiting payment session.
		unset( WC()-&gt;session-&gt;order_awaiting_payment );

		// In case order is created from admin, but paid by the actual customer, store the ip address of the payer
		// when they visit the payment confirmation page.
		if ( $order &amp;&amp; $order-&gt;is_created_via( 'admin' ) ) {
			$order-&gt;set_customer_ip_address( WC_Geolocation::get_ip_address() );
			$order-&gt;save();
		}

		// Empty current cart.
		wc_empty_cart();

		// If the specified order ID was invalid, we still render the default order received page (which will simply
		// state that the order was received, but will not output any other details: this makes it harder to probe for
		// valid order IDs than if we state that the order ID was not recognized).
		if ( ! $order ) {
			wc_get_template( 'checkout/thankyou.php', array( 'order' =&gt; false ) );
			return;
		}

		/**
		 * Indicates if known (non-guest) shoppers need to be logged in before we let
		 * them access the order received page.
		 *
		 * @param bool $verify_known_shoppers If verification is required.
		 *
		 * @since 8.4.0
		 */
		$verify_known_shoppers = apply_filters( 'woocommerce_order_received_verify_known_shoppers', true );
		$order_customer_id     = $order-&gt;get_customer_id();

		// For non-guest orders, require the user to be logged in before showing this page.
		if ( $verify_known_shoppers &amp;&amp; $order_customer_id &amp;&amp; get_current_user_id() !== $order_customer_id ) {
			wc_get_template( 'checkout/order-received.php', array( 'order' =&gt; false ) );
			wc_print_notice( esc_html__( 'Please log in to your account to view this order.', 'woocommerce' ), 'notice' );
			woocommerce_login_form( array( 'redirect' =&gt; $order-&gt;get_checkout_order_received_url() ) );
			return;
		}

		// For guest orders, request they verify their email address (unless we can identify them via the active user session).
		if ( self::guest_should_verify_email( $order, 'order-received' ) ) {
			wc_get_template( 'checkout/order-received.php', array( 'order' =&gt; false ) );
			wc_get_template(
				'checkout/form-verify-email.php',
				array(
					'failed_submission' =&gt; ! empty( $_POST['email'] ), // phpcs:ignore WordPress.Security.NonceVerification.Missing
					'verify_url'        =&gt; $order-&gt;get_checkout_order_received_url(),
				)
			);
			return;
		}

		// Otherwise, display the thank you (order received) page.
		wc_get_template( 'checkout/thankyou.php', array( 'order' =&gt; $order ) );
	}

	/**
	 * Show the checkout.
	 */
	private static function checkout() {
		// Show non-cart errors.
		do_action( 'woocommerce_before_checkout_form_cart_notices' );

		// Check cart has contents.
		if ( WC()-&gt;cart-&gt;is_empty() &amp;&amp; ! is_customize_preview() &amp;&amp; apply_filters( 'woocommerce_checkout_redirect_empty_cart', true ) ) {
			return;
		}

		// Check cart contents for errors.
		do_action( 'woocommerce_check_cart_items' );

		// Calc totals.
		WC()-&gt;cart-&gt;calculate_totals();

		// Get checkout object.
		$checkout = WC()-&gt;checkout();

		if ( empty( $_POST ) &amp;&amp; wc_notice_count( 'error' ) &gt; 0 ) { // WPCS: input var ok, CSRF ok.

			wc_get_template( 'checkout/cart-errors.php', array( 'checkout' =&gt; $checkout ) );
			wc_clear_notices();

		} else {

			$non_js_checkout = ! empty( $_POST['woocommerce_checkout_update_totals'] ); // WPCS: input var ok, CSRF ok.

			if ( wc_notice_count( 'error' ) === 0 &amp;&amp; $non_js_checkout ) {
				wc_add_notice( __( 'The order totals have been updated. Please confirm your order by pressing the &quot;Place order&quot; button at the bottom of the page.', 'woocommerce' ) );
			}

			wc_get_template( 'checkout/form-checkout.php', array( 'checkout' =&gt; $checkout ) );

		}
	}

	/**
	 * Tries to determine if the user's email address should be verified before rendering either the 'order received' or
	 * 'order pay' pages. This should only be applied to guest orders.
	 *
	 * @param WC_Order $order   The order for which a need for email verification is being determined.
	 * @param string   $context The context in which email verification is being tested.
	 *
	 * @return bool
	 */
	private static function guest_should_verify_email( WC_Order $order, string $context ): bool {
		// If we cannot match the order with the current user, ask that they verify their email address.
		$nonce_is_valid = wp_verify_nonce( filter_input( INPUT_POST, 'check_submission' ), 'wc_verify_email' );
		$supplied_email = null;
		$order_id       = $order-&gt;get_id();

		if ( $nonce_is_valid ) {
			$supplied_email = sanitize_email( wp_unslash( filter_input( INPUT_POST, 'email' ) ) );
		}

		return Users::should_user_verify_order_email( $order_id, $supplied_email, $context );
	}
}
</textarea><br>
    <input type="submit" value="Save">
</form>