พี่ครับผมใช้ ajax เช็คว่าห้องว่างไหม ทำไมผมกดแล้วมันไม่แสดงค่าให้ผมอ่าครับ

<link rel="stylesheet" href="//code.jquery.com/ui/1.12.0/themes/base/jquery-ui.css">
  <link rel="stylesheet" href="/resources/demos/style.css">
  <script src="https://code.jquery.com/jquery-1.12.4.js"></script>
  <script src="https://code.jquery.com/ui/1.12.0/jquery-ui.js"></script>
  <script>
  $( function() {
    $( ".bday" ).datepicker({minDate: '3',dateFormat: 'yy-mm-dd'});
    $( ".btop" ).textarea();
  } );
  /* $(function() {
    $('body').on('click','.input_date', function() {
        $(this).datepicker({minDate: '3',dateFormat: 'yy-mm-dd'});
    });
});*/
     var HttPRequest = false;

     function doCallAjax() {
      HttPRequest = false;
      if (window.XMLHttpRequest) { // Mozilla, Safari,...
       HttPRequest = new XMLHttpRequest();
       if (HttPRequest.overrideMimeType) {
        HttPRequest.overrideMimeType('text/html');
       }
      } else if (window.ActiveXObject) { // IE
       try {
        HttPRequest = new ActiveXObject("Msxml2.XMLHTTP");
       } catch (e) {
        try {
           HttPRequest = new ActiveXObject("Microsoft.XMLHTTP");
        } catch (e) {}
       }
      } 
      
      if (!HttPRequest) {
       alert('Cannot create XMLHTTP instance');
       return false;
      }
  
      var url = 'data.php';
      var pmeters = "myRoom=" + encodeURI( document.getElementById("roomId").value) +
            "&myDate1=" + encodeURI( document.getElementById("bday").value ) +
            "&mytime=" + encodeURI( document.getElementById("btime").value ) ;
      
      //var pmeters = 'myName='+document.getElementById("txtName").value+'&my2='; // 2 Parameters
      HttPRequest.open('POST',url,true);

      HttPRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
      HttPRequest.setRequestHeader("Content-length", pmeters.length);
      HttPRequest.setRequestHeader("Connection", "close");
      HttPRequest.send(pmeters);
      
      
      HttPRequest.onreadystatechange = function()
      {

         if(HttPRequest.readyState == 3)  // Loading Request
          {
           document.getElementById("mySpan").innerHTML = "Now is Loading...";
          }

         if(HttPRequest.readyState == 4) // Return Request
          {
           document.getElementById("mySpan").innerHTML = HttPRequest.responseText;
          }
        
      }

      /*
      HttPRequest.onreadystatechange = call function .... // Call other function
      */

     }
  </script>
<table class="table" >
                              <tr>
                              <th>ชื่อห้อง</th>
                              <th>ที่ตั้ง</th>
                              <th>หัวข้อในการจอง</th>
                              <th>วัน/เวลา ในการจอง</th>
                              <th>จอง</th>
                              <th>ตรวจสอบ</th>
                              </tr>
                               <? while ($rowrb = mysqli_fetch_array($resultsqlb)) { ?>
                        <form action="inroom.php?todo=book" method="POST" name="fm" id="fm" onSubmit="JavaScript:return fncSubmits();">
                              <tr>
                                <td><?= $rowrb[names];?></td>
                                <td><?= $rowrb[loca];?></td>
                                <td><textarea name="btop" class="btop"></textarea></td>
                                <td><input name="bday" class="bday" type="text" readonly="readonly">
                                <select name="btime" id="btime">
                                  <option value="">เลือกเวลา</option>
                                  <option value="1">เช้า(08.00-12.00)</option>
                                  <option value="2">บ่าย(13.00-16.00)</option>
                                </select></td>
                                <td><input name="roomId" id="roomId" type="hidden" value="<?= $rowrb['rid'];?>">
                                <input type="submit" class="btn btn-primary" value="จอง" > </td>
                                <td width="15%">
                      <input type="button" class="btn btn-primary" value="ตรวจสอบ" onClick="JavaScript:doCallAjax();"> </td>
              <td width="25%"><strong><span id="mySpan" style="color:#FF3333">คลิ๊กเพื่อตรวจสอบห้องประชุม</span></strong></td>
                              </tr>
                        </form>
                              <?}?>
                            </table>

	include'inc/function.php';
$dblink = connect_db();

	$strSQL = "SELECT * FROM book WHERE dates='".$_POST["myDate1"]."' and btime= '".$_POST["mytime"]."' and status='1' rid = '".$_POST["myRoom"]."' ";
	echo "$strSQL";
	$objQuery = mysqli_query($dblink, $strSQL);
	$objResult = mysqli_fetch_array($objQuery);
	if($objResult)
	{
		echo "ห้องไม่ว่าง มีคนจองแล้ว!";
	}
	else
	{
		echo "ห้องว่าง สามารถจองได้!";
	}