问一个页面将从下拉列表PHP的选定值中加载内容库

EN

<div id="pagetoload"></div>
<form id="fid"  action="">
<select class="input form-control" id="Select" name="Select">
   <option value="Supplier">Supplier</option>
   <option value="User">User</option>
   <option value="Inventory">Inventory</option>
</select>

<button type="submit" name="submit" id="submit" class="btn btn-default" >Submit</button>
</form> 

$(document).ready(function(){

  $("#submit").click(function(){
    $.ajax({
     type: 'POST',
     url: "mysubmitpage.php",
     data: $('#fid').serialize(), 
     success: function(response) {
        //Now here you can get back your html to append in page
        $('#pagetoload').html(response);
     },
    error: function() {
        alert("There was an error submitting form");
    }
 });
});

function actions(that){
document.getElementById('form').action=that.value
console.log(document.getElementById('form').action)
}

<form action="" id="form">
  <select class="input form-control" id="Select" name="Select" onchange="actions(this)">
 <option value="Supplier">Supplier</option>
 <option value="User">User</option>
 <option value="Inventory">Inventory</option>
</select>

  <button type="button" name="submit" class="btn btn-default" onclick="this.form.submit()">Submit</button>
</form>

$(function() {
  $("#submit").click(function() {

    console.log($('#Select').val());
    if ($('#Select').val() == "Supplier") {
      window.open('Supplier.php');
    } else if ($('#Select').val() == "Inventory") {
      window.open('Inventory.php');
    } else if ($('#Select').val() == "User") {
      window.open('User.php');
    }
  });
});

<form action="" id="form">
  <select class="input form-control" id="Select" name="Select">
 <option value="Supplier">Supplier</option>
 <option value="User">User</option>
 <option value="Inventory">Inventory</option>
</select>

  <button type="button" name="submit" id="submit" class="btn btn-default">Submit</button>
</form>
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js"></script>