follow user system

[harman30]

Here I made a another attempt to create a follow user system. I used a table follow_user which has fid as primary key set to Auto_increment and two more columns user_id for id of user to be followed and id_fk for id of user following.

Follow/unfollow button works fine and data gets stored in db but problem is both id_fk and user_id display 0 where they should display id's of user following and user followed instead.

My code is

profile.php

  <div class="follow_box">
   <?php
    if(is_loggedin()){
     $id = $_SESSION['user_login'];
     $userid = $user;
     if($user !=$_SESSION['user_login']) {
     $follow_check="SELECT * from follow_user WHERE id_fk='$id' and user_id='$userid' ";
     $user_sql=mysql_query($follow_check);
     $count=mysql_num_rows($user_sql);
     if($count==0){
      echo "<div id='follow$userid'><a href='' class='follow' id='$userid' style='text-decoration:none;background-color:#3399FF'><span class='btn' style='width:70px;'><b> Follow </b></span></a></div>";
      echo"<div id='remove$userid' style='display:none'><a href='#' class='remove' id='$userid' style='text-decoration:none;'><span class='btn btn-info' style='width:70px;'><b> Following </b></span></a></div>";
      }
      else{
      echo "<div id='follow$userid' style='display:none'><a href='' class='follow' id='$userid'><span class='btn' style='width:70px;'><b> Follow </b></span></a></div>";
      echo"<div id='remove$userid'><a href='#' class='remove' id='$userid'><span class='btn btn-info' style='width:70px;'><b> Following </b></span></a></div>";
      }
      }
      }
       else{
       echo "You must be logged in to view stuff and things";
      }
      ?>

follow.js

   $(function() {
   $(".follow").click(function(){
   var user_id = $(this).attr("id");
   var datastring = 'user_id='+ user_id ;
   $.ajax({
   type: "POST",
   url: "add_follow_user.php",
   data: datastring,
   success: function(html){}
   });
   $("#follow"+user_id).hide();
   $("#remove"+user_id).show();
   return false;
   });
   });
   $(function() {
   $(".remove").click(function(){
   var user_id = $(this).attr("id");
   var datastring = 'user_id='+ user_id ;
   $.ajax({
   type: "POST",
   url: "remove_follow_user.php",
   data: datastring,
   success: function(html){}
    });
   $("#remove"+user_id).hide();
   $("#follow"+user_id).show();
   return false;
   });
   });
   </div>

add_follow_user.php

<?php
    include ( "./inc/header.inc.php" ); 
    if($_POST['user_id']){
    $user_id=$_POST['user_id'];
    $user_id = mysql_escape_String($user_id);
    $sql_in = "INSERT INTO follow_user(id_fk,user_id) VALUES ('$id','$user_id')";
    mysql_query( $sql_in);
    }
    ?>

remove_follow_user.php

<?php
    include ( "./inc/header.inc.php" ); 
    if($_POST['user_id']){
    $user_id=$_POST['user_id'];
    $user_id = mysql_escape_String($user_id);
    $sql_in = mysql_query("DELETE FROM follow_user WHERE id_fk='$id' AND user_id='$user_id'");
    }
    ?>