username check the page - php

Question

I'm creating a system that checks (via AJAX) if a given username is already taken. If so, then it alerts the user accordingly. I'm basing my system off of this tutorial and have tried adapting it to my site.
$(document).ready(function()//When the dom is ready
{
$("#username").change(function()
{ //if theres a change in the username textbox
var username = $("#username").val();//Get the value in the username textbox
if(username.length > 3)//if the lenght greater than 3 characters
{
$("#availability_status").html('<img src="loader.gif" align="absmiddle"> Checking availability...');
//Add a loading image in the span id="availability_status"
$.ajax({ //Make the Ajax Request
type: "POST",
url: "ajax_check_username.php", //file name
data: "username="+ username, //data
success: function(server_response){
$("#availability_status").ajaxComplete(function(event, request){
if(server_response == '0')//if ajax_check_username.php return value "0"
{
$("#availability_status").html('<img src="available.png" align="absmiddle"> <font color="Green"> Available </font> ');
//add this image to the span with id "availability_status"
}
else if(server_response == '1')//if it returns "1"
{
$("#availability_status").html('<img src="not_available.png" align="absmiddle"> <font color="red">Not Available </font>');
}
});
}
});
}
else
{
$("#availability_status").html('<font color="#cc0000">Username too short</font>');
//if in case the username is less than or equal 3 characters only
}
return false;
});
});
ajax_check_username.php - HERE's where I think I'm having problems!!
<?php
include ("inc/db/db.php");
if($stmt = $mysqli->prepare('SELECT NULL FROM `bruger` WHERE `brugernavn` = ?'))
{
$stmt->bind_param('s', $brugernavn);
$brugernavn = $_POST["brugernavn"];
$stmt->execute();
$stmt->store_result();
$count = $stmt->num_rows;
$stmt->close();
if($count = 0)
{
echo '1';
}
else
{
echo '2';
}
}
?>
<tr>
<td><p>Brugernavn</p></td>
<td><input type="text" name="brugernavn" id="username"></td>
<td><span id="availability_status"></span></td>
</tr>
ATTENTION
I think I've made mistakes in my php, so it may be why it does not bother to do what I want it .. but it's just when I think.
This is what my html looking for when I need to check user name in the database. this is how I get no errors at all. it must be said that I never play with ajax or javascript before. so it will be a great help if you could help me further.
Feel free to ask if there is more you want to know something.

Answer 1

This if($count = 0) should be if($count == 0) if that affects your logic.

Answer 2

You're assigning $brugernavn after you're using it.
$stmt->bind_param('s', $brugernavn);
$brugernavn = $_POST["brugernavn"];
Using ajaxComplete is not useful here:
$("#availability_status").ajaxComplete(function(event, request){
You are assigning where you should be comparing:
if($count = 0)
Your Javascript expects a 0 or 1, but your PHP script outputs one of 1 or 2.