title: Why is PHP if(!$_SESSION['username']) is returning false
body: <p>I have been coding a basic PHP Login script just for testing purposes.</p>
  
  <pre><code>&lt;?php
  require 'config.php';
  require 'connect.php';
  
  // username and password sent from form 
  $tbl_name = 'users';
  $username=$_POST['username']; 
  $password=$_POST['password']; 
  
  // To protect MySQL injection (more detail about MySQL injection)
  $username = stripslashes($username);
  $password = stripslashes($password);
  $username = mysqli_real_escape_string($conn, $_POST['username']);
  $password = mysqli_real_escape_string($conn, $_POST['password']);
  $sql="SELECT * FROM $tbl_name WHERE username='$username' and password='$password'";
  $result = mysqli_query($conn, $sql);
  
  // Mysql_num_row is counting table row
  $count = mysqli_num_rows($result);
  
  // If result matched $username and $password, table row must be 1 row
  if($count == 1)
  {
  // Register $username, $password and redirect to file "login_success.php"
  $_SESSION["username"];
  $_SESSION["password"]; 
  header("location:../../home.php");
  }
  else {
  echo "Wrong Username or Password";
  }
  ?&gt;
  </code></pre>
  
  <p>I am able to get through this with no problem, but when it redirects to home.php, here is the code I have to check if session is not registered.</p>
  
  <pre><code>&lt;?php
  session_start();
  if (!$_SESSION['username']) {
  header("location:../../index.php");
  }
  ?&gt;
  </code></pre>
  
  <p>From what I understand, this is supposed to check if the user is not logged in, however when I login it still redirects me to index.php. How can I make sure the session is registered and nothing happens (i.e. I stay on home.php with no redirect, but I'm still logged in.)</p>