AJAX / jQuery发布或获取

Question

我开始基于php，mysql，AJAX和Jquery构建calander。我对后两个方面的知识非常差，但是我愿意学习。我已经找到了基本满足我需要的脚本，但是我有一个关于将其触发到外部文件的问题。

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>serialize demo</title>
  <style>
  body, select {
    font-size: 12px;
  }
  form {
    margin: 5px;
  }
  p {
    color: red;
    margin: 5px;
    font-size: 14px;
  }
  b {
    color: blue;
  }
  </style>
  <script src="https://code.jquery.com/jquery-3.4.1.js"></script>
</head>
<body>

<form>
  <select name="single">
    <option>Single</option>
    <option>Single2</option>
  </select>

  <br>
  <select name="multiple" multiple="multiple">
    <option selected="selected">Multiple</option>
    <option>Multiple2</option>
    <option selected="selected">Multiple3</option>
  </select>

  <br>
  <input type="checkbox" name="check" value="check1" id="ch1">
  <label for="ch1">check1</label>
  <input type="checkbox" name="check" value="check2" checked="checked" id="ch2">
  <label for="ch2">check2</label>

  <br>
  <input type="radio" name="radio" value="radio1" checked="checked" id="r1">
  <label for="r1">radio1</label>
  <input type="radio" name="radio" value="radio2" id="r2">
  <label for="r2">radio2</label>
</form>

<p><tt id="results"></tt></p>

<script>
  function showValues() {
    var str = $( "form" ).serialize();
    $( "#results" ).text( str );
  }
  $( "input[type='checkbox'], input[type='radio']" ).on( "click", showValues );
  $( "select" ).on( "change", showValues );
showValues(); <----- // how to get these values to call an external file (e.g. cal.php?showValues();)
</script>


</body>
</html>

我如何使用AJAX / Jquery将选定的选项发送到外部文件cal.php？...该文件将包含在div中。