dubbio sulla stampa di var di sessione

[Raulken]

<?php 
session_start(); 

//stampa messaggio 
 if(isset($_SESSION['msg'])){ 
echo $_SESSION['msg']; 
unset($_SESSION['msg']); 
                     
               } 
     
   
                
# FileName="Connection_php_mysql.htm" 
# Type="MYSQL" 
# HTTP="true" 
$hostname_connessione = "localhost"; 
$database_connessione = "prova"; 
$username_connessione = "root"; 
$password_connessione = ""; 
$connessione = mysql_pconnect($hostname_connessione, $username_connessione, $password_connessione) or trigger_error(mysql_error(),E_USER_ERROR); 
 ?> 

<?php 
if (!function_exists("GetSQLValueString")) { 
function GetSQLValueString($theValue, $theType, $theDefinedValue = "", $theNotDefinedValue = "") 
 { 
  if (PHP_VERSION < 6) { 
    $theValue = get_magic_quotes_gpc() ? stripslashes($theValue) : $theValue; 
  } 

  $theValue = function_exists("mysql_real_escape_string") ? mysql_real_escape_string($theValue) : mysql_escape_string($theValue);
 
  switch ($theType) { 
    case "text": 
      $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL"; 
      break;     
    case "long": 
    case "int": 
      $theValue = ($theValue != "") ? intval($theValue) : "NULL"; 
      break; 
    case "double": 
      $theValue = ($theValue != "") ? doubleval($theValue) : "NULL"; 
      break; 
    case "date": 
      $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL"; 
      break; 
    case "defined": 
      $theValue = ($theValue != "") ? $theDefinedValue : $theNotDefinedValue; 
      break; 
  } 
  return $theValue; 
} 
} 
?> 
<?php 
// *** Validate request to login to this site. 

if(!isset($_SESSION['id'])){ 
     
$loginFormAction = $_SERVER['PHP_SELF']; 
if (isset($_GET['accesscheck'])) { 
  $_SESSION['PrevUrl'] = $_GET['accesscheck']; 
} 

if (isset($_POST['mod_email'])) { 
  $loginUsername=$_POST['mod_email']; 
  $password=md5($_POST['mod_password']); 
  $MM_fldUserAuthorization = ""; 
  $MM_redirectLoginSuccess = "prova.php"; 
  $MM_redirectLoginFailed = "prova.php?failed"; 
  $MM_redirecttoReferrer = true; 
  mysql_select_db($database_connessione, $connessione); 
   
  $LoginRS__query=sprintf("SELECT email, password FROM utenti WHERE email=%s AND password=%s",
     GetSQLValueString($loginUsername, "text"), GetSQLValueString($password, "text")); 
     
  $LoginRS = mysql_query($LoginRS__query, $connessione) or die(mysql_error()); 
  $loginFoundUser = mysql_num_rows($LoginRS); 
  if ($loginFoundUser) { 
     $loginStrGroup = ""; 
     
    if (PHP_VERSION >= 5.1) {session_regenerate_id(true);} else {session_regenerate_id();}
     //declare two session variables and assign them 
    $_SESSION['MM_Username'] = $loginUsername; 
    $_SESSION['id'] = $loginUsername; 
    $_SESSION['MM_UserGroup'] = $loginStrGroup;     
    $_SESSION['msg']="OK";       

    if (isset($_SESSION['PrevUrl']) && true) { 
      $MM_redirectLoginSuccess = $_SESSION['PrevUrl'];     
    } 
     
    header("Location: " . $MM_redirectLoginSuccess ); 
  } 
  else { 
      $_SESSION['msg']="KO"; 
    header("Location: ". $MM_redirectLoginFailed ); 
  } 
}?> 

<form action="<?php echo $loginFormAction; ?>" method="POST" name="login" id="form-login" >
                                                            <fieldset class="input">
                                                             <p id="form-login-email">
                                                              <label for="modlgn_email">Email</label>

                                                              <input id="modlgn_email" type="text" name="mod_email" class="inputbox" alt="email" size="18" />
                                                             </p> 
                                                            <p id="form-login-password">
                                                              <label for="modlgn_password">Password</label>

                                                              <input id="modlgn_password" type="password" name="mod_password" class="inputbox" size="18" alt="password" />
                                                             </p> 
                                                            
                                                              <span class="art-button-wrapper">
                                                                   <span class="art-button-l"> </span>
                                                                   <span class="art-button-r"> </span>
                                                                   <input type="submit" name="Submit" class="art-button" value="Login" />
                                                               </span> 
                                                           </fieldset> 
                                                           
                                                          </form> 
                                           
                                                  <div class="cleared"></div> 
                                              </div> 
                                          </div> 
                                  <div class="cleared"></div> 
                              </div> 
                          </div> 
                          <?php 
}else{ 


// ** Logout the current user. ** 
$logoutAction = $_SERVER['PHP_SELF']."?doLogout=true"; 
if ((isset($_SERVER['QUERY_STRING'])) && ($_SERVER['QUERY_STRING'] != "")){ 
  $logoutAction .="&". htmlentities($_SERVER['QUERY_STRING']); 
} 

if ((isset($_GET['doLogout'])) &&($_GET['doLogout']=="true")){ 
  //to fully log out a visitor we need to clear the session varialbles 
  $_SESSION['MM_Username'] = NULL; 
  $_SESSION['MM_UserGroup'] = NULL; 
  $_SESSION['PrevUrl'] = NULL; 
  $_SESSION['id'] = NULL; 
  unset($_SESSION['MM_Username']); 
  unset($_SESSION['MM_UserGroup']); 
  unset($_SESSION['PrevUrl']); 
  unset($_SESSION['id']); 
     
  $logoutGoTo = "prova.php"; 
  if ($logoutGoTo) { 
    header("Location: $logoutGoTo"); 
    exit; 
  } 
} 
?> 
[url="<?php echo $logoutAction ?>"]Esegui logout[/url]  
<?php 
} 


/*/stampa msg 
 if(isset($_SESSION['msg'])){ 
echo $_SESSION['msg']; 
unset($_SESSION['msg']); 
/*/ 
?>

perchè

if(isset($_SESSION['msg'])){
echo $_SESSION['msg'];
unset($_SESSION['msg']);

se lo metto in cima me lo stampa e se lo metto in fondo non me lo stampa?