问设置条带支付网关时返回json数据时出错。未捕获(在promise中) SyntaxError:意外的标记<在JSON中的位置0

EN

var buyBtn = document.getElementById('payButton');
var responseContainer = document.getElementById('paymentResponse');

// Create a Checkout Session with the selected product
var createCheckoutSession = function(stripe) {
  return fetch("stripe_charge.php", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      checkoutSession: 1,
    }),
  }).then(function(result) {
    return result.json(); // JSON PASSED FROM HERE
  });
};

// Handle any errors returned from Checkout
var handleResult = function(result) {
  if (result.error) {
    responseContainer.innerHTML = '<p>' + result.error.message + '</p>';
  }
  buyBtn.disabled = false;
  buyBtn.textContent = 'Buy Now';
};

// Specify Stripe publishable key to initialize Stripe.js
var stripe = Stripe('<?php echo STRIPE_PUBLISHABLE_KEY; ?>');

buyBtn.addEventListener("click", function(evt) {
  buyBtn.disabled = true;
  buyBtn.textContent = 'Please wait...';


  createCheckoutSession().then(function(data) { // TO HERE - ERROR IS HERE
    if (data.sessionId) {
      stripe.redirectToCheckout({
        sessionId: data.sessionId,
      }).then(handleResult);
    } else {
      handleResult(data);
    }
  });
});

checkout.php:1 Uncaught (in promise) SyntaxError: Unexpected token < in JSON at position 0