funzione _GET e _POST

[mybox]

ciao ragazzi ho un problemino...cioè vorrei cambiare una cosa a un file...
ho uno script che quando uno scrive un messaggio nella barra del link x inviarlo riscrive tutto il testo e se questo è lungo a volte crea problemi...dovrebbe essere la funzione get o post da cambiare...sapete dirmi se vi allego il file dove cambiarla????

<?php 

$title = 'Nuovo topic'; 
require 'pmheader.php'; 

$sub = (empty($_POST['sub'])) ? "0" : $_POST['sub']; 
$txt = (empty($_POST['txt'])) ? "0" : $_POST['txt']; 
$forum = (empty($_POST['forum'])) ? "-1" : $_POST['forum']; 

echo $header; 

if(!$userdata['session_logged_in']) 
{ 
    echo "Spiacente devi essere loggato per postare un nuovo topic. Clicca <anchor>Qui!<go href=\"" . append_sid("waplogin.$phpEx") . "\" /></anchor>"; 
} 


else if($sub == "0" || $txt == "0" || $forum == "-1") 
{ 
?> 
Oggetto: <input name="sub" type="text" emptyok="false"/>
 
Messaggio: <input name="txt" emptyok="false"/>
 
Forum: <select name="forum"> 
<option value="-1">Scegli il forum</option> 
<?php 
     
    $query = $db->sql_query("select forum_id,forum_name from ". FORUMS_TABLE . " where forum_status = \"0\" order by cat_id ASC"); 
    $forum = $db->sql_fetchrowset($query); 
    foreach ($forum as $val) 
    { 
        $auth = auth(AUTH_ALL,$val['forum_id'],$userdata); 
        if($auth['auth_post']) 
        { 
            echo "<option value=\"".$val['forum_id']."\">".htmlentities ($val['forum_name'])."</option>\n"; 
        } 
    } 


?> 
</select>
 
<anchor> 
    Invia
 
    <go href="<?php echo append_sid("wapnew.$phpEx?sub=$(sub)&amp;txt=$(txt)&amp;forum=$(forum)"); ?>" method="post"> 
        <postfield name="sub" value="$(sub)"/> 
        <postfield name="txt" value="$(txt)"/> 
        <postfield name="forum" value="$(forum)"/> 
    </go> 
</anchor> 
<?php 
} 
else 
{ 
    $current_time = time(); 
    $sql = $db->sql_query("SELECT * FROM " . USERS_TABLE . " WHERE username = '" . str_replace("\'", "''", $userdata['username']) . "'"); 
    $userdata = $db->sql_fetchrow($sql); 
    $user_id = $userdata['user_id']; 
    if( $userdata['user_level'] != ADMIN && $board_config['board_disable'] ) 
    { 
        echo "Mi spiace ma il forum e\'disattivato. Visita il sito web in un\' altro momento"; 
    } 
    else { 
                $sql = "SELECT forum_status FROM " . FORUMS_TABLE . " WHERE forum_id = \"$forum_id\""; 
                $query = $db->sql_query($sql); 
                $forum_status = $db->sql_fetchrow($query); 
                $auth = auth(AUTH_ALL,$forum_id,$userdata); 
                if ( $forum_status['forum_status'] == FORUM_LOCKED && !$auth['auth_mod']) 
                    { 
                    $footer = "

<anchor>Forum Home<go href=\"" . append_sid("wap.$phpEx") . "\" /></anchor>".$footer; 
                    echo "Mi spiace questo forum e\' chiuso. Non puoi postare nel topic."; 
                    die(" ".$footer); 
                    } 
                    else 
                    { 
                        //Flood Control 
                        $current_time = time(); 
                        $query  = $db->sql_query("SELECT MAX(post_time) AS last_post_time FROM " . POSTS_TABLE . " WHERE poster_id = \"$user_id\""); 
                        $flood = $db->sql_fetchrow($query); 
                        if ( $flood['last_post_time'] > 0 && ( $current_time - $flood['last_post_time'] ) < $board_config['flood_interval'] ) 
                        { 
                            echo "Non puoi inviare un messaggio subito. Aspetta un po e riprova."; 
                        } 
                        else 
                        { 
                            $txt = $txt." \n\n[i]Scritto da Nokia Mobile Device[/i]"; 
                            $uid = make_bbcode_uid(); 
                            $txt = prepare_wap_post($txt,$uid); 
                            $time = time(); 
                            $update_topics = $db->sql_query("insert into " . TOPICS_TABLE . " (forum_id, topic_title, topic_poster, topic_time, topic_views, topic_replies, topic_status, topic_vote, topic_type, topic_first_post_id, topic_last_post_id, topic_moved_id) values (\"$forum\", \"$sub\", \"$user_id\", \"$time\", \"0\", \"0\", \"0\", \"0\", \"0\", \"0\",\"0\", \"0\")"); 
                            $topic = $db->sql_nextid(); 
                            $update_posts = $db->sql_query("insert into " . POSTS_TABLE . " (topic_id, forum_id, poster_id, post_time, poster_ip, enable_bbcode, enable_html, enable_smilies, enable_sig, post_edit_count) values (\"$topic\",\"$forum\",\"".$userdata['user_id']."\",\"$time\",\"".$userdata['user_ip']."\",\"0\",\"0\",\"1\",\"$sig\",\"0\")"); 
                            $post_id = $db->sql_nextid(); 
                            $update_topics2 = $db->sql_query("update ". TOPICS_TABLE . " set topic_first_post_id = \"$post_id\", topic_last_post_id = \"$post_id\" where topic_id = \"$topic\""); 
                            $update_text = $db->sql_query("insert into " . POSTS_TEXT_TABLE . " (post_id, bbcode_uid, post_subject, post_text) values (\"$post_id\", \"$uid\", \"$sub\", \"$txt\")"); 
                            $update_forums = $db->sql_query("update " . FORUMS_TABLE . " set forum_posts=forum_posts+1, forum_last_post_id = $post_id, forum_topics=forum_topics+1 where forum_id = \"$forum\""); 
                            $update_user = $db->sql_query("update " . USERS_TABLE . " set user_posts=user_posts+1 where user_id = \"$user_id\""); 
                            echo "Clicca <anchor>Qui!<go href=\"". append_sid("waptopic.$phpEx?topic=$topic&amp;forum=$forum") . "\" /></anchor> per vedere il tuo messaggio."; 
                        } 
                    } 
                } 
            } 
echo $footer; 
?>

mi potete aiutare a correggere il tutto????

grazie 1000