Passing variables through 3 pages - php

Question

I've spent a lot of time looking for something that could help me doing this:
I have 3 pages, one called login.php, another called trataLogin.php and another called index.php.
The login and trataLogin page is working perfectly but when I try to call a variable into the index.php from login I can't do it.. I don't know what else to do it.
This is my login.php
<?php
require_once('connection/dbconnection.php');
session_start();
?>
...
<form name="form" action="trataLogin.php" method="post">
<input type="text" name="username" placeholder="username" /><br/>
<input type="password" name="password" placeholder="password" /><br/>
<br/>
<br/>
<input type="submit" value="login" />
</form>
trataLogin.php
<?php
require_once('connection/dbconnection.php');
session_start();
$_SESSION['dadoslogin']=$_POST;
$username = $_POST['username'];
$password = sha1($_POST['password']);
$query = "SELECT * FROM utilizadores WHERE username = '" . $username . "' AND password = '" . $password . "'";
$admin='';
$result = $conn->query($query);
if ($result->num_rows > 0) {
$_SESSION['verifica_login'];
$row = $result->fetch_assoc();
if ($row['admin'] == 1) {
$admin = true;
header('Location:admin.php');
} elseif($row['admin'] == 0){
$admin = false;
header('Location:index.php');
} else {
$_SESSION['verifica_login']="Username ou password incorretos";
}}
?>
and in index.php I have this
<?php
require_once('connection/dbconnection.php');
session_start();
$_SESSION['dadoslogin']=$_POST;
?>
and somewhere below in index.php I've something that it was suppose to print the username of the person who logged in
<?php echo $_SESSION['username']; ?>

Answer 1

You're overwriting your $_SESSION in index.php:
Remove that part
$_SESSION['dadoslogin']=$_POST;
And echo your variable like this:
echo $_SESSION['dadoslogin']['username'];