php - Boostrap Select

It doesn't show output <option>. It shows only the select with no element inside. I'm using bootstrap-select library. What's the problem?

  $(function () {
    $('select').selectpicker();
  });
<!-- BOOTSTRAP -->
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css" integrity="sha384-Vkoo8x4CGsO3+Hhxv8T/Q5PaXtkKtu6ug5TOeNV6gBiFeWPGFN9MuhOf23Q9Ifjh" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.4.1.slim.min.js" integrity="sha384-J6qa4849blE2+poT4WnyKhv5vZF5SrPo0iEjwBvKU7imGFAV0wwj1yYfoRSJoZ+n" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js" integrity="sha384-Q6E9RHvbIyZFJoft+2mJbHaEWldlvI9IOYy5n3zV9zzTtmI3UksdQRVvoxMfooAo" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js" integrity="sha384-wfSDF2E50Y2D1uUdj0O3uMBJnjuUD4Ih7YwaYd1iqfktj0Uod8GCExl3Og8ifwB6" crossorigin="anonymous"></script>

<link rel="stylesheet" href="./css/timeline.css">

<!-- ICONE -->
<script src="https://kit.fontawesome.com/6b765b0f40.js" crossorigin="anonymous"></script>

<!-- SELECT WITH SEARCH BAR -->
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-select@1.13.14/dist/css/bootstrap-select.min.css">
<script src="https://cdn.jsdelivr.net/npm/bootstrap-select@1.13.14/dist/js/bootstrap-select.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap-select@1.13.14/dist/js/i18n/defaults-*.min.js"></script>

<select class="selectpicker">
  <option>Mustard</option>
  <option>Ketchup</option>
  <option>Relish</option>
</select>

Answer

Solution:

You don't have any problem: It's working here: enter image description here

Try to set the function like this (inside script tag):

  <script type="text/javascript">
    $(function () {
      $('select').selectpicker();
    });
  </script>

Source