Salve, vorrei passare come attributo value del tag input una variabile php. Di seguito riporto il codice php e successivamente quello HTML
Codice PHP:
<?php
session_start
(); //memorizzare UID nella variabile di sessione

$_SESSION['ID']=$riga[UID];

session_write_close(); /*da chiudersi appena memorizzate le variabili di sessione
                 permette di fare eseguire alla sessione più operazioni in pipeline
             (ad esempio la visualizzazione dei risultati di query diverse su più pagine)*/



$mysqli = new mysqli('localhost','root','','DB');
if (
mysqli_connect_error())
    die(
"Errore durante la connessione");

if (isset(
$_POST['submit']))
{
    if (isset(
$_POST['username']) && isset($_POST['password']) && $_POST['username'] != '' && $_POST['password'] != '')
    {
            
$username $_POST['username'];
            
$password $_POST['password'];
            
            
//SQL Injection
            
$username stripslashes($username);
            
$password stripslashes($password);
            
$username $mysqli->real_escape_string($username);
            
$password $mysqli->real_escape_string($password);


            
$risultato $mysqli->query("SELECT UID, UserName, Password, DataScadenza FROM Account WHERE UserName = '$username' AND Password = sha1('$password')"); //sha1 on query
            
$riga $risultato->fetch_assoc();

            
$data date("Y-m-d H:i:s");
            
$scadenza $riga[DataScadenza];
            
$data1 strtotime($data);
            
$data2 strtotime($scadenza);

            if (
$username == $riga[UserName])
            {
                if (
strlen($password)>=8)
                {    
                        if (
$data1 <= $data2)
                        {
                            
header('Location: [url]http://localhost/prova/home.php[/url]');
                            
$risultato->close();
                        }
                        else
                        {    
                            
$errore='Account scaduto - Per maggiori informazioni contattare l\'amministratore';
                            
$risultato->close();
                        }
                }
                else
                {
                    
$errore='Password non valida (minimo 8 caratteri)'//account.php
                    
$risultato->close();
                }
            }
            else
            {
                
$risultato->close();
                
header('Location: [url]http://localhost/prova/loginerr.php[/url]');
            }
    }
    else
    {
        if(isset(
$risultato))
            
$risultato->close(); //tale oggetto è definito fino a questo punto
        
header('Location: [url]http://localhost/prova/loginerr.php[/url]');
    }
}    
if(isset(
$errore))
    echo
"$errore";
$mysqli->close();
?>
<?php
include("control.php");
?>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Errore durante il login</title>
<style type="text/css">
body,p,a,span,div,input,legend,h1,h2,h3,h4,h5,h6,l i,dd,dt,th,td{
font-family:Arial, Helvetica, sans-serif;
}
body,p,a,span,div,input,legend,li,dd,dt,th,td{
font-size:10pt;
}
#loginform {
width:300px;
margin:auto;
}
#loginform fieldset{
padding:10px;
}
#loginform legend{
font-weight:bold;
font-size:9pt;
}
#loginform label{
display:block;
height:2em;
background-color:#E7E7E7;
padding:10px 10px 0;
}
#loginform input {

margin-right:20px;
border:1px solid #999999;
float:right;
clear:right;
background:#CCCCCC;
}
#loginform input:focus,#loginform input:hover {
border:1px solid #333333;
}
.error{
color:red;
}
.centrato{
display:block;
position:absolute;
top:50%;
left:50%;
margin:-150px 0 0 -150px;
}

</style>

</head>
<body>
<div class="centrato">
<form id="loginform" method="post" action="<?php $_SERVER['PHP_SELF']?>">
<fieldset>
<legend>Nome utente o password errati!</legend>



Inserisci nome utente e password per accedere al portale</p>
<div class="error"><label for="username"><input type="text" name="username" tabindex="1" id="username" value="<?php if(isset($_POST['username'])) echo $_POST['username']; else echo"errore"; ?>" />username:
</label>
<label for="password"><input type="password" name="password" tabindex="2" id="password" />password:
</label>
</div>
<label for="submit">
<input name="submit" type="submit" id="submit" tabindex="4" value="Log in" />
</label>
</p>

</fieldset>
</form>
</div>
</body>
</html>

Purtroppo la variabile $_POST['username'] non risulta definita? Come mai? Qualche soluzione?