PHP中的表单操作语句

I've got following problem with my PHP code: my form is divided into two divs: first div shows up when the page is opened, second div displays after clicking a button (and this first one, thanks to Ajax, hides). My plan is to check a few statements, if true then create POST, get from it data and then dynamically create table, switching the content using Ajax again. BUT. I cannot use the 'action' thing because of the statements. When I've got 'submit' type - it creates POST, but reloads the page. If I replace it with 'button' type - Ajax works, but POST is empty. Here's my code:

     function formu ($w="1", $sr="on", $comma="", 
     $space ="",  $other =""){?>
     <form id="options"  action="" method="POST" >
     <div id = "first">
     <h1 id = "title"> Choose a file </h1>
     <input type = "radio" name="radio" id ="radio" value="op1" class ="radio"> ONE
     <br>
     <input type ="radio" name="radio" id="radio" value ="op2" class = "radio"> TWO
     <br>
     <input type ="radio" name="radio" id="radio" value="op3" class = "radio"> THREE
    <br>
    <input type = "button" id="Submit" Value = "Show">
    </div>
    <div id = "sec">
    <h1 id = "title2"> Choose options </h1>
    <p id="odwiersza"> Cut: </p> 
    <input type="text" name="w" value=""> <br>
    <p id="Separators"> Separator: </p>
    <input type = "checkBox" name="sr"> sr 
    <input type= "checkBox" name="comma"> comma
    <input type = "checkBox" name = "space"> space  
    <input type = "checkBox" name ="other"> other (which?) <input type="text" name="such">
    <br>
    <input type="submit" id="choose" value = "Enter"> 
   </div>
   </form>
   <?php } 
   formu();

   ?>
   <div id= "here"> </div>

And then my ideas:

    if($_SERVER["REQUEST_METHOD"] == "POST"){
    $w = $_POST['w'];
    $sr = $_POST['sr'];
    $comma = $_POST['comma'];
    $space = $_POST['space'];
    $other = $_POST['other'];

     if (empty($w) || !($sr || $comma || $space || $other)){
         echo "You have to enter the number and choose at least one separator!";

   } else {
        **/*  here I've tried:
         ?> <script>
         window.location = 'third.php';  //but it doesn't create POST table
         </script> 
         <?php 
         require_once("third.php"); //but it attaches value with reloading the page, so first div shows up above my table
         include "third.php"; //same as above
        */**
 }
 }

I've also tried Ajax script but it doesn't work as well:

    <script>
    var SubmitBtn2 = document.getElementById('choose');
    SubmitBtn2.onclick = function(){
        var formularz = document.getElementById('sec');
        formularz.style.display = 'none';
        var formularz1 = document.getElementById('first');
        formularz1.style.display = 'none';
        var title2 = document.getElementById('title2');
        $(title2).hide();
        var FormData = {plik: "<?php echo $_POST['radio']; ?>",
                        wiersz: "<?php echo $_POST['w']; ?>",
                        średnik: "<?php echo $_POST['sr']; ?>",
                        przecinek: "<?php echo $_POST['comma']; ?>",
                        spacja: "<?php echo $_POST['space']; ?>",
                        inne: "<?php echo $_POST['other']; ?>",
                        jakie: "<?php echo $_POST['such']; ?>"};
        $(document.getElementById('back')).hide();
        $.ajax({
        type: 'POST',
        url: "third.php",
        data: FormData,
        complete: function (reply) {
            $.ajax({
                type: 'POST',
                url: "third.php",
                complete: function (reply) {
                $('here').append(reply);

                }
            });
    }
  });
    }
    </script>

EDIT: I've tried to use event.preventDefault(); and now my code looks as below:

        $(document.getElementById('choose')).click(function()
        {   event.preventDefault();
                    $.ajax({
                url : $(this).attr('action') || window.location.pathname,
                type: "POST",
                data: $(this).serialize(),
                success: function (data) {
                    $.get("test5new.csv", function(data) {
                var build = '<table border="1" cellpadding="2" cellspacing="0" width="100%">
';
                var rows = data.split("
");
                var cut = rows.slice(<?php echo $w; ?>); //ponieważ tablice liczy się od 0 
                cut.forEach( function getvalues(thisRow) {
                    build += "<tr>";
                    var columns = thisRow.split("<?php echo $pattern; ?>");
                    for(var i=0;i<columns.length;i++){ build += "<td>" + columns[i] + "</td>"; }            
                build += "</tr>";
                })
                build += "</table>";
                $(document.getElementById('wrap')).append(build);   

            });
                },
        error: function (jXHR, textStatus, errorThrown) {
            alert(errorThrown);
        }
    });

        }); 

but, although it does not refresh, it doesn't create POST neither. Please please help.