ho questa pagina di registrazione:
Codice PHP:
<?php
session_start();
if (isset($_SESSION['autorizzato'])) {
    echo "

Effettua il logout</p>";
    echo '[url="index.php"]Home[/url] | ';
    echo '[url="logout.php"]Logout[/url]';
    die;
}
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
        <script src="script.js" type="text/javascript"></script>
        <title>Registrazione</title>
    </head>
    <body>
        [url="index.php"]Home[/url]
        <form method="post" name="inserisci" action="#" onsubmit="return validate(this);">
            <table>
                <tr>
                    <td>User:</td>
                    <td><input type="text" name="user" /></td>
                </tr>
                <tr>
                    <td>Email:</td>
                    <td><input type="text" name="email" /></td>
                </tr>
                <tr>
                    <td>Password:</td>
                    <td><input type="password" name="pass" /></td>
                </tr>
                <tr>
                    <td><input type="submit" name="registra" value="Registrati"/></td>
                </tr>
            </table>
        </form>
        <?php
        include("config.php");
        $link = mysql_connect($host, $user, $password) or die("Non è possibile connettersi al server
");
        $conn = mysql_select_db($db, $link) or die("Non è possibile connettersi al db
");
        $user = mysql_real_escape_string($_POST['user']);
        $email = mysql_real_escape_string($_POST['email']);
        $pass = mysql_real_escape_string($_POST['pass']);
        $query = "insert into utenti values ('" . $user . "','" . $email . "','" . $pass . "')";
        $controllo = "select * from utenti where nome='" . $user . "'";
        $result = mysql_query($controllo);
        $riga = mysql_fetch_row($result);
        if (isset($_POST['registra'])) {
            if ($user == null || $email == null || $pass == null) {
                echo "Dati mancanti";
            }
            if ($riga[0] != "") {
                echo "Utente gia esistente";
            } else {
                mysql_query($query, $link) or die(mysql_error($link));
                $_SESSION['autorizzato'] = $user;
//                echo '<script language="javascript">document.location.href="index.php"</script>';
            }
        }
        ?>
    </body>
</html>
ho messo su anche uno script per il controllo del form in js:
Codice PHP:
function validate(form){
    fail = validateUser(form.user.value);
    fail += validateEmail(form.email.value);
    fail += validatePassword(form.pass.value);
    if(fail==""){
        return true;
    } else {
        alert(fail);
        return false;
    }
}

function validateUser(field){
    if(field == ""){
        return "Nessun Username inserito.\n";
    } else if(field.length < 5){
        return "Lo username deve avere almeno 4 lettere.\n"
    } else if(/[^a-zA-Z0-9_-]/.test(field)){
        return "Sono ammessi solo caratteri a-z, A-Z, 0-9, - e _.\n";
    }
    return "";
}

function validateEmail(field){
    if(field == ""){
        return "Nessuna Email inserita.\n";
    } else if(!((field.indexOf(".") > 0) && (field.indexOf("@")) ||/[^a-zA-Z0-9.@_-]/.test(field))){
        return "L'indirizzo email non è valido.\n";
    }
    return "";
}

function validatePass(field){
    if(field == ""){
        return "Nessuna Password inserita.\n";
    } else if(field.length < 5){
        return "La password deve avere almeno 5 caratteri.\n";
    } else if(!/[a-z]/.test(field) || !/[A-Z]/.test(field) || !/[0-9]/.test(field)){
        return "Sono richiesti i caratteri a-z, A-Z e 0-9.\n";
    }
    return "";
} 
ovviamente nn riesco a far funzionare entrambi.
come posso fare per amalgamare i due codici?