Admin and User same log in form?

Hello everyone! I am a student and still a noob in PHP. Well, I'm trying to figure out what is the best method for a log in page system that provide the ability for an Administrator to log in using the same log in form for normal users but get redirected to a administrator page if the system recognize as Admin and normal users redirected to users page. Any idea? Any help would be greatly appreciated! :) Here is my log in code for users -->

<?php
    //Start session
    session_start();

    //Include database connection details
    require_once('voting_connect.php');

    //Array to store validation errors
    $errmsg_arr = array();

    //Validation error flag
    $errflag = false;

    //Connect to mysql server
    include('voting_connect.php');
{


    //Select database
    $db = mysql_select_db($db);
    if(!$db) {
        die("Unable to select database");
    }

    //Function to sanitize values received from the form. Prevents SQL injection
    function clean($str) {
        $str = @trim($str);
        if(get_magic_quotes_gpc()) {
            $str = stripslashes($str);
        }
        return mysql_real_escape_string($str);
    }

    //Sanitize the POST values
    $s_ID = clean($_POST['s_ID']);
    $s_Password = clean($_POST['s_Password']);

    //Input Validations
    if($s_ID == '') {
        $errmsg_arr[] = 'ID number missing';
        $errflag = true;
    }
    if($s_Password == '') {
        $errmsg_arr[] = 'Password missing';
        $errflag = true;
    }

    //If there are input validations, redirect back to the login form
    if($errflag) {
        $_SESSION['ERRMSG_ARR'] = $errmsg_arr;
        session_write_close();
        header("location: login.php");
        exit();
    }

    //Create query
    $qry="SELECT * FROM students WHERE s_ID='$s_ID' AND s_Password='$s_Password'";
    $result=mysql_query($qry);

    //Check whether the query was successful or not
    if($result) {
        if(mysql_num_rows($result) == 1) {
            //Login Successful
            session_regenerate_id();
            $member = mysql_fetch_assoc($result);
            $_SESSION['SESS_MEMBER_ID'] = $member['s_ID'];
            $_SESSION['SESS_FIRST_NAME'] = $member['s_FirstName'];
            $_SESSION['SESS_LAST_NAME'] = $member['s_LastName'];

            session_write_close();
            header("location: vote.php");
            exit();
        }else {
            //Login failed
            header("location: logfail.php");
            exit();
        }
    }else {
        die("Query failed");
    }
    }
?>