Vettore $_FILES non popolato

[lyllo]

ciao gente.
sto sbattendo la testa su un problema che si presenta all'invio di files sullo spazio web del server che ospita il sito.
in locale tutto funziona benissimo, sul server NO.
il vettore rimane sempre VUOTO.

<?php
ini_set('error_reporting',E_ALL);

include_once('conn.inc.php');

$id = $_GET['_addpic'];
$base_dir = "attach/";

$sel_img = "<select name='tipo'><option value='1'>Copertina</option><option value='0' selected>Generale</option></select>";
echo "<fieldset style='width:50%'><legend> Modulo aggiunta immagini alla scheda del velivolo</legend>
<form enctype=\"multipart/form-data\" name='add_pic' method='POST' action='mod_pic.php?_addpic=$id'>
        <input type='hidden' name='MAX_FILE_SIZE' value='8388608' /> 
        <input type='file' name='add_p'>
        $sel_img
        <input type='submit' name='sub_pic' value='Aggiungi immagine'>
    </form><font style='font-size: 10pt'>
    Ricorda di impostare almeno un'immagine come [b]Copertina[/b] ovvero come immagine che verrà visualizzata di fianco al link nella pagina principale. Scegline una evocativa!.</font></fieldset>
    
<fieldset style='width:50%'>[url='pagine.php?mod=$id']Torna alla scheda del velivolo[/url]</fieldset><hr style='align: center; width: 70%'>";

...

if(isset($_POST['sub_pic']) && $_POST['sub_pic'] == 'Aggiungi immagine' ){
echo "<pre>";
print_r($_FILES);
    $id = $_GET['_addpic'];
    $tipo = $_POST['tipo'];    
    $img = $_FILES['add_p']['name'];

    if($_FILES['add_p']['error'] == 0){
        
        

    $ext = $_FILES['add_p']['type'];
echo "ESTENSIONE: ".$ext;
    $uploadedfile = $_FILES['add_p']['tmp_name'];
    $up_dir = $base_dir.$img;
    
    list($width,$height) = getimagesize($uploadedfile);

    if($ext == "image/pjpeg" || $ext == "image/jpeg"){
        $src = imagecreatefromjpeg($uploadedfile);
        }
    elseif($ext == "image/x-png" || $ext == "image/png"){
        $src = imagecreatefrompng($uploadedfile);
        }
    elseif($ext == "image/gif"){
        $src = imagecreatefromgif($uploadedfile);
        }

    $newwidth = 200;
    $newheight = ($height/$width)*200;
    $tmp = imagecreatetruecolor($newwidth,$newheight);
    imagecopyresampled($tmp,$src,0,0,0,0,$newwidth,$newheight,$width,$height);
    $thumb_path= $base_dir."/thumbs/".$img;
    imagejpeg($tmp,$thumb_path,80);

    imagedestroy($src);
    imagedestroy($tmp);     
    
    if(copy($uploadedfile,$up_dir)){
        $q = mysql_query("INSERT INTO attach (id_velivolo, tipo, path) 
                    VALUES 
                ('$id', '$tipo', '$img') ") or die(mysql_error());
        if($q){
            header("Location: mod_pic.php?_addpic=$id");
            }
        }
    }
}

[lyllo]

configurazione del php 5.2.6 del server su cui sono ospitato:

PHP Version 5.2.6

System Linux gracchus.sui-inter.net 2.4.21-47.ELsmp #1 SMP Wed Jul 5 20:38:41 EDT 2006 i686
Build Date Aug 19 2008 14:09:32
Configure Command './configure' '--host=i686-redhat-linux-gnu' '--build=i686-redhat-linux-gnu' '--target=i386-redhat-linux-gnu' '--program-prefix=' '--prefix=/usr' '--exec-prefix=/usr' '--bindir=/usr/bin' '--sbindir=/usr/sbin' '--sysconfdir=/etc' '--datadir=/usr/share' '--includedir=/usr/include' '--libdir=/usr/lib' '--libexecdir=/usr/libexec' '--localstatedir=/var' '--sharedstatedir=/usr/com' '--mandir=/usr/share/man' '--infodir=/usr/share/info' '--cache-file=../config.cache' '--with-libdir=lib' '--with-config-file-path=/etc' '--with-config-file-scan-dir=/etc/php.d' '--disable-debug' '--with-pic' '--disable-rpath' '--without-pear' '--with-bz2' '--with-curl' '--with-exec-dir=/usr/bin' '--with-freetype-dir=/usr' '--with-png-dir=/usr' '--enable-gd-native-ttf' '--without-gdbm' '--with-gettext' '--with-gmp' '--with-iconv' '--with-jpeg-dir=/usr' '--with-openssl' '--with-png' '--with-expat-dir=/usr' '--with-zlib' '--with-layout=GNU' '--enable-exif' '--enable-ftp' '--enable-magic-quotes' '--enable-sockets' '--enable-sysvsem' '--enable-sysvshm' '--enable-sysvmsg' '--enable-track-vars' '--enable-trans-sid' '--enable-yp' '--enable-wddx' '--with-kerberos' '--enable-ucd-snmp-hack' '--with-unixODBC=shared,/usr' '--enable-memory-limit' '--enable-shmop' '--enable-calendar' '--enable-dbx' '--enable-dio' '--without-mime-magic' '--without-sqlite' '--with-libxml-dir=/usr' '--with-xml' '--with-system-tzdata' '--with-apxs2=/usr/sbin/apxs' '--without-mysql' '--without-gd' '--without-odbc' '--disable-dom' '--disable-dba' '--without-unixODBC' '--disable-pdo' '--disable-xmlreader' '--disable-xmlwriter' '--disable-json' '--without-pspell'
Server API Apache 2.0 Handler
Virtual Directory Support disabled
Configuration File (php.ini) Path /etc
Loaded Configuration File /etc/php.ini
Scan this dir for additional .ini files /etc/php.d
additional .ini files parsed /etc/php.d/bcmath.ini, /etc/php.d/dbase.ini, /etc/php.d/dom.ini, /etc/php.d/gd.ini, /etc/php.d/imap.ini, /etc/php.d/json.ini, /etc/php.d/mbstring.ini, /etc/php.d/mcrypt.ini, /etc/php.d/mysqli.ini, /etc/php.d/mysql.ini, /etc/php.d/pdo.ini, /etc/php.d/pdo_mysql.ini, /etc/php.d/soap.ini, /etc/php.d/sqlite.ini, /etc/php.d/xmlreader.ini, /etc/php.d/xmlrpc.ini, /etc/php.d/xmlwriter.ini, /etc/php.d/xsl.ini, /etc/php.d/zip.ini
PHP API 20041225
PHP Extension 20060613
Zend Extension 220060519
Debug Build no
Thread Safety disabled
Zend Memory Manager enabled
IPv6 Support enabled
Registered PHP Streams php, file, data, http, ftp, compress.bzip2, compress.zlib, https, ftps, zip
Registered Stream Socket Transports tcp, udp, unix, udg, ssl, sslv3, sslv2, tls
Registered Stream Filters string.rot13, string.toupper, string.tolower, string.strip_tags, convert.*, consumed, convert.iconv.*, bzip2.*, zlib.*

[lyllo]

risolto l'arcano: dio abbia in gloria i programmatori della Pannel Plesk.
il problema è che per ragioni misteriose e sconosciute nella versione "Site Preview" sessioni e $_FILES non funzionano.
per quanto ho scoperto.