<?php

        if ($_SERVER["REQUEST_METHOD"] == "POST")
{

        $user="admin";
        $pass="neehahs";
        $host="localhost";
        $db="login";

         $con=mysqli_connect($host,$user,$pass,$db);
                  if(mysqli_connect_errno($con)){
       echo "Failed to connect to MySQL: " . mysqli_connect_error();
      }


        $username=($_POST['username']);
        $password=md5($_POST['password']);

        $username = mysqli_real_escape_string($con,$username);
        $password = mysqli_real_escape_string($con,$password);




        $sql="SELECT * FROM members WHERE student_id='%$username%' AND student_pass='%$password%'";
        $sqldata=mysqli_query($con,$sql)
        or die ("error");

        while ($row=mysqli_fetch_array($sqldata)){

        if($row["user_type"]=='student'){
    header('location: http://localhost/greenstudio/index.html');

        }

elseif
    ($row["user_type"]=='organizer'){
    header('location: http://localhost/greenstudio/index2.html');

    }else {
        echo"Sorry, your credentials are not valid, Please try again.";


    }
    }
    exit();
        }

          ?>

Table: users
--------+----------+----------+----------
user_id | username | password | user_type
--------+----------+----------+----------
1       | admin    | neehahs  | organizer
2       | student1 | mypass   | student

SELECT
  user_type
FROM
  users
WHERE
  BINARY username='$username' AND
  BINARY password='$password'

<?php

if ($_SERVER["REQUEST_METHOD"] == "POST"){
    $user="admin";
    $pass="neehahs";
    $host="localhost";
    $db="login";
    $con=mysqli_connect($host,$user,$pass,$db);
    if(mysqli_connect_errno($con)){
        echo "Failed to connect to MySQL: " . mysqli_connect_error();
    }
    $username=($_POST['username']);
    $password=md5($_POST['password']);
    $username = mysqli_real_escape_string($con,$username);
    $password = mysqli_real_escape_string($con,$password);
    $sql="SELECT user_type FROM members WHERE BINARY student_id='$username' AND BINARY student_pass='$password'";
    $sqldata=mysqli_query($con,$sql) or die ("error");
    $row = mysqli_fetch_array($sqldata);
    if(is_null($row) || mysqli_num_rows($sqldata)!=1){
        echo "Sorry, your credentials are not valid or matches more than 1 user, Please try again.";
    } else if(isset($row["user_type"])){
        if($row["user_type"]=='student'){
            header('location: http://localhost/greenstudio/index.html');
        } else if($row["user_type"]=='organizer'){
            header('location: http://localhost/greenstudio/index2.html');
        } else {
            echo "User type was returned as not student nor organizer.";
        }
    } else {
        echo "Sorry, user_type was not returned in the dataset retrieved from the database.";
    }
}

?>