php code not working correctly? - php

Question

At
"$query = ("SELECT * FROM `accounts` WHERE username = '$username'")or die(mysql_error());"
If I don't add accounts, id then "$_SESSION['userid'] = $row['id'];" wont work but if I do add it then login wont work also accounts is the database and id is inside of it.
<?php
session_start();
if(isset($_SESSION['users']) != ""){
echo '<script type="text/javascript">','index();','</script>';
}
require '../php/dbConnect.php';
$username = $_POST['username'];
$password = $_POST['password'];
$query = ("SELECT * FROM `accounts` WHERE username = '$username'")or die(mysql_error());
$response = mysql_query($query);
$row = mysql_fetch_array($response);
if($row['password'] == md5($password))
{
$_SESSION['online'] = true;
$_SESSION['users'] = $username;
$_SESSION['userid'] = $row['id'];
echo '<script type="text/javascript">','redirect();','</script>';
}
else{
echo("Wrong Credentials");
}
?>
<div id="friend-request-title" class="overlay round-edge panel-left">
<label class="w3-text-white "><h2><b>Friend Requests</b></h2></label>
</div>
<div id="friend-request-panel" class="overlay round-edge panel-up">
<?php
require 'php/dbConnect.php';
$query = ("SELECT * FROM `accounts` WHERE `id` <> '".$_SESSION['userid']."'");
$response = mysql_query($query);
while($row = mysql_fetch_assoc($response)) {
echo '
<div class="lesson-section">
<div class="container">
<img id="profile-image" src="img/profile2.png" class="big-circle float" style="margin: 4% 0 0 0;">
</div>
<label id="" class="w3-text-white"><h4><b>You have a new friend request.</b></h4></label>
<label id="" class="w3-text-white">Friend request from '. $row['username'] .'.</label>
<br>
<button id="" class="w3-btn w3-text-white light-overlay border-remove round-edge" style="margin: 2% 2% 0 0;" type="button"><b>Accept</b></button>
<button id="" class="w3-btn w3-text-white light-overlay border-remove round-edge" style="margin: 2% 0 0 0;" type="button"><b>Decline</b></button>
</div>
<hr>
';
}
?>

Answer 1

You have error in this part of your php:
if(isset($_SESSION['users']) != ""){
echo '<script type="text/javascript">','index();','</script>';
}
You should use isset then check if not empty
if(isset($_SESSION['users']) && $_SESSION['users'] != ""){
echo '<script type="text/javascript">','index();','</script>';
}