如何将数据复选框从ajax发送到php

<form id="myForm">
  <input type="checkbox" id="checkbox1" value="value1"> Option 1
  <input type="checkbox" id="checkbox2" value="value2"> Option 2
  <input type="checkbox" id="checkbox3" value="value3"> Option 3
  <button type="button" onclick="sendData()">Submit</button>
</form>

<script>
function sendData() {
  var checkboxes = document.querySelectorAll('input[type="checkbox"]:checked');
  var values = [];
  checkboxes.forEach(function(checkbox) {
    values.push(checkbox.value);
  });

  var xhr = new XMLHttpRequest();
  xhr.open("POST", "process.php", true);
  xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
  xhr.onreadystatechange = function() {
    if (xhr.readyState === 4 && xhr.status === 200) {
      // 处理响应
      console.log(xhr.responseText);
    }
  };
  xhr.send("data=" + JSON.stringify(values));
}
</script>

<?php
$data = json_decode($_POST['data']);
// 处理接收到的数据
foreach ($data as $value) {
  echo $value . "<br>";
}
?>