Jquery compelete function not working - jquery-ui

Question

I m very much new to the jQuery and AJAX technology. I am trying to create a form which will insert the values in the database without refresh the page. Most of the code are working as expected. But among there are two case which is not working as expected.
I am fetching values through checkbox. When I select only one checkbox it works but when I select multiple checkbox, the value stored in the database as Array.
I want to display a message once the form data submitted succesfully but its not working.
Please find the below respective code for the same.
Jquery:
$('#add').click(function(){
var domain_type = $('#domain').val();
var domain_zone = $('#domain_zone').val();
var client_name = $('#client_name').val();
//var language[] = "";
var lang = new Array();
if(language==1){
//alert("You select one language");
valid = true;
lang = "English";
}else{
//alert("You select multiple language");
var i =0;
$.each($('input[name=lang]:checked'), function(){
lang.push($(this).val());
});
var count = lang.length;
if(count ==1){
alert("You need to select two languages");
var valid = false;
}else if(count>2){
alert("You can select only two languages");
var valid = false;
}else{
valid = true;
}
}
var formMsge = $('#formStatus');
$('#formStatus').html('<img src="./img/loader.gif"> Please wait while adding the data in database.');
$.ajax({
type: "POST",
url: "./test/test.php",
data: {domain_type:domain_type, domain_zone:domain_zone, client_name:client_name, 'lang[]':lang},
success:function(conf){
$('#formStatus').ajaxComplete(
function(event,request){
if(conf=="OK"){
$('#formSuccess').show();
$('#addClient').hide();
}else{
$('#formError').show();
$('#forError').text("Please try again");
}
}
);
}
});
return false;
});
test.php:
include('../../classes/access_user/all.class.inc.php');
echo $workstream->addClient()
;
php class file:
public function addClient(){
$domain_type = isset($_POST['domain_type'])?$_POST['domain_type']:'';
$domain_zone = isset($_POST['domain_zone'])?$_POST['domain_zone']:'';
$client_name = isset($_POST['client_name'])?$_POST['client_name']:'';
$lang = isset($_POST['lang'])?$_POST['lang']:'';
$add_by = 'Robindra Singha';
$add_on = date("Y-m-d");
if(isset($domain_type) || isset($domain_zone) || isset($client_name) || isset($lang)){
$sql = "INSERT INTO client_list (domain_type_id, client_name, domain_zone, language, add_on, add_by, last_update_on, last_update_by) VALUES('$domain_type','$client_name','$domain_zone','$lang','$add_on','$add_by','$add_on','$add_by')";
$res = mysql_query($sql) or die(mysql_error());
if(mysql_inserted_id() != 0){
$msg = "OK";
}else{
$msg = "System face an issue while adding client details!";
}
}else{
$msg = "System face an issue while adding client details, please try again!";
}
return $msg;
}
In above code, my issue is checkbox value are not able to pass when I select the multiple checkbox, second I am not able to display any text once the form is successfully submit. Except this two issues, my code able to insert the information successfully. I would be glad if any one guide me in completing the work properly. Thank you in advance for your kind support.
Note: I am not able to add the HTML file as i paste here, it display as normal text. please suggest.