<div class="popup">
 <tr><select id="a1_title"></select></div></tr>
 <tr><select id="a2_title"></select></div></tr>
        <!-- Button (Double) -->
        <div class="form-group">
        <label class="col-md-4 control-label" for="cancel"></label>
        <button type="button" id="cancel" class="btn btn-default cancel">Cancel</button>
        <button type="submit" id="save" class="btn btn-success submit">OK</button>
        </div>
        </div>
    <div id="map" class="map"><div>

// JavaScript Document
        $(document).ready(function(){
               $.getJSON("php/drpdwn.php", success = function(data){
                    var items="";
                    for(var i = 0; i< data.length; i++){
                        // RETAIN JSON KEY AS OPTION VALUE, JSON VALUE AS OPTION TEXT                items +="<option value='"+data[i].id+"'>" + data[i].name+"</option>";
                    }
                    $("#a1_title").append(items);
                    $("#a1_title").change();
                });
               $("#a1_title").change(function(){

                  // OBTAIN SELECTED VALUE
                  var selectedValue = $(this).find(":selected").text();

                   if( selectedValue == "Landuse/landcover") {

                      $.getJSON("php/lulc_db.php",success = function(data){
                          var items="";
                          for(var i = 0; i< data.length; i++){

                              items+="<option value='"+data[i]+"'>" + data[i] +"</option>";
                          }
                          // REMOVE PREVIOUS ITEMS
                          var myNode = document.getElementById("a2_title");
                          while (myNode.firstChild) {
                              myNode.removeChild(myNode.firstChild);
                          }
                          // ADD NEW ITEMS
                          $("#a2_title").append(items);
                      });
                      $("#a2_title").change(function(){
                    //the main problem start from here
//this the only one which is not working
                        var selectedtext = $(this).find(":selected").text();
                         if( selectedValue == "Built Up") {
                             alert("k");
                        $('input[type="submit"]').on('click',function(){
           $.getJSON("php/geojson.php?layer="+ $(this).text(),success = function(data){
    console.log(data);
            });
        });          }
                         });

                  }
                  else if( selectedValue == "Soil") {

                      $.getJSON("php/soil_db.php",success = function(data){
                          var items="";
                          for(var i = 0; i< data.length; i++){

                              items+="<option value='"+data[i]+"'>"+data[i]+"</option>";

                          }
                          // REMOVE PREVIOUS ITEMS
                          var myNode = document.getElementById("a2_title");
                          while (myNode.firstChild) {
                              myNode.removeChild(myNode.firstChild);
                          }
                          // ADD NEW ITEMS
                          $("#a2_title").append(items);
                      });
                                }

                });

              });

<?php
if(isset($_GET["layer"]))
   {
$host = "localhost";
$user = "postgres";
$pass = "admin";
$db = "Querybuilderdb";
$con = pg_connect("host=$host dbname=$db user=$user password=$pass")
    or die ("Could not connect to servern");
$sql = "SELECT gid, level_1 , st_asgeojson(geom) AS geojson FROM  pachgaon_lulc where level_1='{$layer}'  ";
$rs = pg_query($con, $sql);
if (!$rs) {
    echo "An SQL error occured.n";
    exit;
}
# Build GeoJSON feature collection array
$geojson = array(
   'type'      => 'FeatureCollection',
   'features'  => array()
);

# Loop through rows to build feature arrays
while ($row = pg_fetch_array($rs)) {

    $properties = $row;
    # Remove geojson and geometry fields from properties
    unset($properties['geojson']);
    $feature = array(
         'type' => 'Feature',
         'id' => $row['gid'],
         'properties' => array(
          'name' => $row['level_1']
          ),

         'geometry' => json_decode($row['geojson']),
    );
    array_push($geojson['features'], $feature);
}
header('Content-type: application/json');
echo json_encode($geojson);
}
?>