Chained Select Boxes (Country, State, City)

$(‘#mobile_phone_network option:selected’).val()i didn’t tested but it should work. It’s simple and it will give you some idea

**HTML**
<div id="countryWrap"><select id="country" name="country"></select></div>
<div id="stateWrap"><select id="state" name="state"></select></div>
<div id="cityWrap"><select id="city" name="city"></select></div>

<script>
$(document).ready(function(){
  $('#country').change(function(){
    loadState($(this).find(':selected').val())
  })
  $('#state').change(function(){
    loadCity($(this).find(':selected').val())
  })


})

function loadCountry(){
        $.ajax({
            type: "POST",
            url: "ajax/ajax.php",
            data: "get=country"
            }).done(function( result ) {
                $(result).each(function(){
                    $("#country").append($('<option>', {
                        value: this.id,
                        text: this.name,
                    }));
                })
            });
}
function loadState(countryId){
        $("#state").children().remove()
        $.ajax({
            type: "POST",
            url: "ajax/ajax.php",
            data: "get=state&countryId=" + countryId
            }).done(function( result ) {
                $(result).each(function(){
                    $("#state").append($('<option>', {
                        value: this.id,
                        text: this.name,
                    }));
                })
            });
}
function loadCity(stateId){
        $("#city").children().remove()
        $.ajax({
            type: "POST",
            url: "ajax/ajax.php",
            data: "get=city&stateId=" + stateId
            }).done(function( result ) {
                $(result).each(function(){
                    $("#city").append($('<option>', {
                        value: this.id,
                        text: this.name,
                    }));
                })
            });
}

// init the countries
loadCountry();
</script>




**ajax.php** 

$countryId = isset($_POST['countryId'])  ? $_POST['countryId'] : 0;
$stateId = isset($_POST['stateId'])  ? $_POST['stateId'] : 0;
$command = isset($_POST['get'])  ? $_POST['get'] : "";

switch($command){
case "country":
$statement = "SELECT id, name FROM country";
break;
case "state":
$statement = "SELECT id, name FROM state WHERE country_id=".(int)countryId;
break;
case "city":
$statement = "SELECT id, name FROM country WHERE state_id=".(int)stateId;
break;
default:
break;
}

$sth = $dbh->prepare($statement);
$sth->execute();
$result = $sth->fetchAll();

echo json_encode($result);
exit();