How to set user/admin accounts for a redirect after log in? PHP

I have had look around stack overflow and a few other similar sites, and noticed there are a few people asking the same question as me but for them it works.

I'm new to php so excuse me if I have made some errors, my main problem with this code is that the IF statement which is deciding what page to go to seems to default to index.php. I have made a login table in MySQL already and have username/password column, and another column with a boolean value which states if the user is admin.

I have no idea why this doesn't work but hopefully I can get some help. Thanks for you

<?php
session_start(); // Starting Session
    $error=''; // Variable To Store Error Message
        if (isset($_POST['submit'])) {
        if (empty($_POST['username']) || empty($_POST['password'])) {
    $error = "Username or Password is invalid";
    }
else
    {
// Define $username and $password
      $username=$_POST['username'];
    $password=$_POST['password'];

// Establishing Connection with Server by passing server_name, user_id and password as a parameter
      $connection = mysql_connect(" ", " ", " ", " ");

// Selecting Database
    $db = mysql_select_db(" ", $connection);

// SQL query to fetch information of registerd users and finds user match.
    $query = "SELECT * FROM login WHERE username='$username' and password='$password'";
    $result=mysql_query($query) or die(mysql_error());
    $row= mysql_fetch_array($result);
    $count=mysql_num_rows($result);

$auth=$row['admin'];
if($count==1){
    if($auth['admin']==1){
        session_start();
        $_SESSION['admin']=$auth;
        $_SESSION['username']=$username;
        header("location: member.php");
    }
    elseif($auth['admin']==0){
        session_start();
        $_SESSION['admin']=$auth;
        header("location:index.php");
    }
    } else {
    $error = "Username or Password is invalid";
    }
    mysql_close($connection); // Closing Connection
    }
}
?>