controller not sending data back to ajax request codeigniter - ajax

Question

I have developed a login system using ajax the problem is when i send the ajax request everything is working and validating fine i just need to pass data back to my ajax request I am using echo json_encode("true"); but somehow it is just echoing the value true in the controller and not going back in the view!
HTML
<form onsubmit="return validate()" method="post" action="<?php echo base_url(); ?>admin/admin_login">
<input class="md-input" placeholder="username" type="text" name = 'login_username' id = 'login_username' />
<input class="md-input" placeholder="password" type="password" name= 'login_password' id= 'login_password' />
<button type='submit' class="btn btn-primary btn-block btn-large">Login</button>
</form>
AJAX
<script>
function validate(){
if(!$("#login_username").val()){
alert("username is required");
return false;
}
if(!$("#login_password").val()){
alert("Password is required");
return false;
}
return true;
var data={
"login_username" : $("#login_username").val(),
"login_password" : $("#login_password").val()
};
$.ajax({
type: 'post',
url: '<?=base_url()?>Admin/admin_login',
dataType: 'json',
data:data,
success: function (data) {
if(data=="true"){
alert("ok");
}
else
{
alert("not ok");
}
}
});
}
</script>
admin_login controller
public function admin_login(){
$data = $this->input->post();
$status=$this->admin_validate->validate($data);
if($status){
$session=array(
"admin"=>$this->input->post("login_username"),
);
$this->session->set_userdata($session);
//redirect("Admin/contact");
header('Content-Type: application/json');
echo json_encode("true");
}
else
{
header('Content-Type: application/json');
echo json_encode("false");
//redirect("Admin");
}
}

Answer 1

Now iam going to change the code little
change the HTML form to
<form>
<input class="md-input" placeholder="username" type="text" name = 'login_username' id = 'login_username' />
<input class="md-input" placeholder="password" type="password" name= 'login_password' id= 'login_password' />
<button type='button' onclick="validate()" class="btn btn-primary btn-block btn-large">Login</button>
</form>
and Now change your ajax to
<script>
function validate(){
if(!$("#login_username").val()){
alert("username is required");
return false;
}
if(!$("#login_password").val()){
alert("Password is required");
return false;
}
$.ajax({
type: 'post',
url: '<?php echo base_url()."Admin/admin_login"; ?>',
data:{ "login_username" : $("#login_username").val(), "login_password" : $("#login_password").val() },
success: function (data) {
if(data=="true"){
alert("ok");
}
else
{
alert("not ok");
}
}
});
}
</script>
and your controller to
public function admin_login(){
$data = $this->input->post();
$status=$this->admin_validate->validate($data);
if($status){
$session=array(
"admin"=>$this->input->post("login_username"),
);
$this->session->set_userdata($session);
echo "true";
}
else
{
echo "false";
}
}
Hope this helps you. :)

Answer 2

Have you tried sending true or false without the quotation marks?, if not try creating an array and then passing it to the echo json_encode(); something like:
$result = array();
array_push($result, true);
echo json_encode($result);
on your ajax you will have to read it as follow
if(data[0] == true){
alert("Ok");
}else{
alert("Not OK");
}
Hope it helps

Answer 3

you are returning true in the script so the form is get submitted. no ajax call occurs.
<script>
function validate(){
if(!$("#login_username").val()){
alert("username is required");
return false;
}
if(!$("#login_password").val()){
alert("Password is required");
return false;
}
return true; // HERE THE ISSUE //
var data={
"login_username" : $("#login_username").val(),
"login_password" : $("#login_password").val()
};
$.ajax({
type: 'post',
url: '<?=base_url()?>Admin/admin_login',
dataType: 'json',
data:data,
success: function (data) {
if(data=="true"){
alert("ok");
}
else
{
alert("not ok");
}
}
});
}