php click out logged user with ajax - php

Question

good afternoon from gmt+8 timezone.
I had built a login/system , now I want to implement a function that will click out users , so i make a status column in the db ,
2 types of values , lock => lock , active => not lock.
I can use crud method to update the status and output in a table. surely i cam lock the user , and status change to lock, that is working fine, but the problem is the locked user still has access the to system , since the session still valid , she/he has to close the browser or their session is terminated.
on the login page I check if user is lock then can login.
since the user still has access when the session still valid , I want to input ajax call the server to check the status on setInterval.
on backend php: check if user is lock , terminate the session , give alerts box and redirect.
but the issue now is my code is not working， here are my ajax call , if I un-comment //console.log('success');, success will be kept in console.log , meaning the call is success.
<script>
function getUserStatus(){
$.ajax({
type: "POST",
url: 'ajax/ajax.php',
data: {username: '<?php echo $_SESSION['admin_username'] ;?>' },
success: function(response){
//console.log('success');
}
});
}
setInterval(function(){
getUserStatus();
},3000);
</script>
on my ajax.php page , I make sure connection to db is working,
if ($_SERVER["REQUEST_METHOD"] == "POST") {
$admin_username = check_input($_POST['username']);
if( isLocked($admin_username) ){
session_destroy();
echo "<script>window.alert('you had been clicked out');window.location.href='../index.php';</script>";
}
}
function to check user is lock
function isLocked($username){
global $connection ;
$query = "SELECT status FROM table where name = '$username' ";
$result = mysqli_query($connection,$query);
confirm($result);
while( $row = fetch_array($result)){
if($row['status'] == 'locked' ){
return true;
}else{
return false;
}
}
}
if i directly access ajax.php with the log user , below action is working .
if( isLocked($admin_username) ){
session_destroy();
echo "<script>window.alert('you had been clickedout');window.location.href='../index.php';</script>"; }
not sure what is wrong with my codes and how to fix it ?
any assistance/suggestion would be highly appreciated .

Answer 1

your ajax.php echos something, that may be data, a json or in your case a js script.
The ajax calls ajax/ajax.php, if the http request succeeds it enters
success:
function(response){
//console.log('success');
}
so the variable response holds the output of that call to ajax/ajax.php. if you use
$.ajax({
type: "POST",
url: 'ajax/ajax.php',
dataType: "script",
data: {username: '<?php echo $_SESSION['admin_username'] ;?>' },
success: function(response){
//console.log('success');
}
the value of "response" will be executed if it is a working script.(without tags)
further information you can find here:
http://api.jquery.com/jQuery.ajax/
without dataType: "script",in the call you could do something like that:
function(response){
//console.log('success');
$('#somediv').html(response);
}
that will insert the result in a div, if it is a well formated js script, it will be executed.