Checking if database row exists using jQuery

Question

I'm busy on a register form, but the biggest part is jQuery. So I wanna validate the inputs using jQuery too. After lots of thinking, this is what I came up with;

$('#usernameDone').click(function() 
    {
        $.post('public/robin/check_existing.php',{value: $("#username").val()}, function(data){
window.alert(data);
if(data == true){
    window.alert("Name exists");
}else{
    window.alert("Name doesnt exist");
}
    });

(I know the 'click' function isn't closed, but that's because there's some stuff after it.)

So it posts the value of the #username input field into check_existing.php , which looks like this;

<?php
$value = $_POST['value'];
$db = new MySQLi('127.0.0.1', 'root', '*******', 'htv1.1');
$query = $db->prepare('SELECT * FROM ht_users WHERE naam = ?');
$query->bind_param('s', $value);
$query->execute();
if ($query->num_rows > 0) 
{
    return true;
}
else
{
    return false;
}

Please note this is not the method I normally use. This was more like a 'testbench'.

The only thing is; it always returns one empty alert box, and then it shows 'name doesnt exist'.

How can I solve this problem?

Answer 1

In your case, the return statement in PHP is just stopping execution. You need to send the data to the actual response, eg using echo :

if ($query->num_rows > 0) 
{
    echo "true";
}
else
{
    echo "false";
}

The first javascript alert is blank as no data is being returned from PHP, which evaluates as false .

Answer 2

Change the PHP to read

if ($query->num_rows > 0) 
{
    echo "true";
}
else
{
    echo "false";
}

Then the JS to read

if(data == "true"){

Answer 3

I think you are using $.POST wrong. 'data' can never have any value in your code. It is and will be undefined.

Look at the code from the documentation: http://api.jquery.com/jquery.post/

Here is a snipped that should work:

$.post( "ajax/test.html", function( data ) {
  alert(data);
  // Go ahead with your code.
});

So use an anonymous function that takes (data) and proceed from there.