PHP - Setting Session Var From Form In Recordset

<?php
session_start();


/* clear all session variable */
$_SESSION = array();

/* set a session variable for later use */
$_SESSION['what_page'] = "admin00";
?>

if(!isset($_SESSION['what_page']) || $_SESSION['what_page'] != "index.php") {
	$_SESSION = array();
	session_destroy();
	header("Location: index.php");	
	exit();
}

Notice: Undefined index: loggedIn in C:\xampp\htdocs\Login\index.php on line 11

Notice: Undefined index: loggedIn in C:\xampp\htdocs\Login\index.php on line 17
You must be logged in to view this page!

<?php

session_start();

error_reporting(E_ALL | E_NOTICE);

ini_set('display_errors', '1');

require 'connect.php';

if($_SESSION['loggedIn'] == 1) {

	//Do Nothing

	exit();
	
} else if($_SESSION['loggedIn'] != 1) {

	echo "You must be logged in to view this page!";

	exit();
}

if($_SESSION['user_level'] == -1) {

	header("Location: banned.php");

} if(isset($_SESSION['username'])) {

	echo "<div id='welcome'> Welcome, ". $_SESSION['username'] ." <br> </div> ";

}

?>

<?php
error_reporting(E_ALL | E_NOTICE);

require 'connect.php';

session_start();

if (isset($_POST['submit'])) {
   
    $username = trim($_POST['username']);
    $password = trim($_POST['password']);
   
    if (empty($username)) {
       
        echo "You did not enter a username, Redirecting...";
       
        echo "<meta http-equiv='refresh' content='2' URL='login.php'>";
       
        exit();
       
    }
   
    if (empty($password)) {
       
        echo "You did not enter a password, Redirecting...";
       
        echo "<meta http-equiv='refresh' content='2' URL='login.php'>";
       
        exit();
       
    } 
   
    //Prevent hackers from using SQL Injection to hack into Database
    $username = mysqli_real_escape_string($con, $_POST['username']);
    $password = mysqli_real_escape_string($con, $_POST['password']);

	$result = $con->query("SELECT * FROM $tbl_name WHERE username='$username' AND password='$password'");

	$row = $result->fetch_array();

	$user_level = $row['user_level'];


// check to make sure query did execute. If it did not then trigger error use mysqli::error to see why it failed
if($result->num_rows > 0)
{

//Set default user
	$_SESSION['loggedIn'] == 1;
	$_SESSION['user_level'] == 1;
	$_SESSION['username'] == trim($_POST['username']);
	header("Location: index.php");
	exit();	
} else if($row['user_level'] == 1) {

		$_SESSION['user_level'] == 1;

		//Location admin 
		header("Location: admin.php");

		exit();

	} else if($row['user_level'] == -1) {

		$_SESSION['user_level'] == -1;

		$_SESSION['username'] == trim($_POST['username']);

		//Location banned
		header("Location: banned.php");

		exit();
	} else if($_SESSION['loggedIn'] == true) {

		//Location default user home page
		header("index.php");
	} else {

		echo "Invalid Username/Password";
	}


  //Kill unwanted session
} if(isset($_POST['killsession'])) {

	session_destroy();
	echo "<br> <br> The Session Destroyed. (Basically means you have been logged out)";
	exit();

	}

?>