Va bene, proviamo così

Codice PHP:
<?php
    session_start
(); 
    include(
"config/settings.php"); 

    if (isset(
$_SESSION["logged"])) 
    { 
        
//header('Location: config/admin.php'); 
        
var_dump($_SESSION);
        echo 
'Session set here, click [url="config/admin.php"]here[/url]';
        exit(); 
    } 

    if (isset(
$_POST['submit'])) 
    { 
        
$username $_POST["username"]; 
        
$password $_POST["password"]; 
          
        
//Check if password is correct 
        
if($password == $gallery_password && $username == $gallery_username
        { 
            
$_SESSION["logged"] = "true"
            
//header('Location: config/admin.php'); 
            
var_dump($_SESSION);
            echo 
'Logged in, data set, click [url="config/admin.php"]here[/url]';
            exit(); 
        } 
        else 
        { 
            
$error="Password & username was incorrect, please try again"
            unset(
$_SESSION["logged"]); 
        } 
    } 
?> 

<link rel="stylesheet" href="style.css" type="text/css" /> 
<form id="form1" name="form1" method="post" action=""> 
  <table width="500" border="0" align="center" cellpadding="5"> 
    <tr> 
      <td width="174"><div align="right">[b]Username:[/b]</div></td> 
      <td width="300"><label> 
        <input name="username" type="text" id="username" /> 
      </label></td> 
    </tr> 
    <tr> 
      <td><div align="right">[b]Password:[/b]</div></td> 
      <td><input name="password" type="password" id="password" /></td> 
    </tr> 
    <tr> 
      <td></td> 
      <td><label> 
        <input type="submit" name="Submit" value="Login" /> 
      </label></td> 
    </tr> 
  </table> 
</form> 
<?php if (isset($error)) echo $error?>

e nel admin.php ci metti prima di if(isset($_SESSION["logged"])){
Codice PHP:
var_dump($_SESSION);