How to make like and unlike - mysql

Question

I have tried to make like and like system using ajax and mysql.
Click like, like is added and Click again, like min 1.
I want, when I click unlike, it will back to like.
But this, unlike until minus..
This is my mysql
<?php
include 'connect.php';
session_start();
$ip=$_SESSION['id'];
if ($_POST['id'])
{
$id=$_POST['id'];
$ip_sql=mysql_query("select id_user from social where track_id='$id' and id_user='$ip'");
$count=mysql_num_rows($ip_sql);
if ($count==0)
{
$sql = "update track set jumlah_like=jumlah_like+1 where track_id='$id'";
mysql_query($sql);
$sql_in = "insert into social (id_user,track_id) values ('$ip','$id')";
mysql_query($sql_in);
$result=mysql_query("select jumlah_like from track where track_id='$id'");
$row=mysql_fetch_array($result);
$love=$row['jumlah_like'];
?>
<span class="broke_love" align="left"><?php echo $love; ?></span>
<?php
}
else
{
$sql = "update track set jumlah_like=jumlah_like-1 where track_id='$id'";
mysql_query($sql);
//$sql_in = "insert into social (id_user,track_id) values ('$ip','$id')";
//mysql_query($sql_in);
$result=mysql_query("select jumlah_like from track where track_id='$id'");
$row=mysql_fetch_array($result);
$love=$row['jumlah_like'];
echo "<span class=on_img align=left>$love</span>";
}
}
?>

Answer 1

The problem is algorithmic that is causing your button to be stuck on 'unlike'.
Your basic condition is: if ($count==0) which always returns greater than 0 after the statement $sql_in = "insert into social (id_user,track_id) values ('$ip','$id')"; is run.
Therefore, your code gets stuck in always executing the else, and continously diminishing the likes.
You need to change your logic to be more:
Check if likes exist and add for specific user.
If like already exists, remove like record.

Answer 2

I think you are missing something from your script as you do not appear to remove a record from the table social.
However most of your selects and updates can be done with a single piece of SQL. Something
like:-
UPDATE track a
LEFT OUTER JOIN social b ON a.track_id = b.track_id AND id_user='$ip'
SET a.jumlah_like = a.jumlah_like + IF(b.track_id IS NULL, 1, -1)
It would probably be better to have a votes table rather than adding and deleting records on the social table. One row per vote.