Undefined variable: PHP_SELF

[micio1980]

Rieccomi,
Ho questo script preso da freephp.it per rispondere ad un sondaggio.
Quello per inserire il sondaggio l'ho risolto grazie all'aiuto di Daniele.
Adesso non volevo rompere ulteriormente ma dopo svariati tentativi e letture di vari post sull'argomento sono riuscito ad evitere alcuni Notice ma alla fine mi da il seguente errore:

Notice: Undefined variable: PHP_SELF in C:\siti\prova\sonda\vote.php on line 71
questa è la linea 71

  echo "<font face=\"Verdana\" size=\"1\"><a href=\"".$PHP_SELF."?results=1\" target=\"_blank\">View results</a></font>"; 

Questo è l'intero script

<?
 require_once("settings.inc");
 $poll = mysql_connect("$db_host", "$db_username", "$db_password")
        or die ("Could not connect");
 mysql_select_db ("cerebus")
        or die ("Could not select database");
        
     $checkforcurrent = mysql_query("select id,dateactive from polls where active='yes' order by question limit 1");
     $current_poll = mysql_fetch_row($checkforcurrent);
     $curpollid = $current_poll[0];
     $dateactive = $current_poll[1];
     $today=date("Y-m-d 00:00");
     $date1=strtotime( "$dateactive 00:00" );
     $date2=strtotime("$today");
     $datediffer = (($date2-$date1)/86400);
     
 if ($datediffer>=$interval){
     $lookfornext = mysql_query("select id from polls where active='no' order by id limit 1");
     $getnextid = mysql_fetch_row($lookfornext);
     $nextpollid = $getnextid[0];
     if ($nextpollid){
          $date = date("Y-m-d");
          mysql_query("update polls set active='end' where id=$curpollid");
          mysql_query("update polls set active='yes', dateactive='$date' where id=$nextpollid");
          mysql_query("delete from poll_ip");
     }
 }

 function writeresults (){
     $getquestion = mysql_query("select id,question,votes from polls where active='yes' order by question limit 1");
     $question = mysql_fetch_row($getquestion);
     echo "<font face=\"Verdana\" size=\"2\">[b]".$question[1]."[/b]

";
     $totalvotes = $question[2];
     $getresults = mysql_query("select votes, alternative from poll_alternatives where poll_id='$question[0]'");
     $imageid=1;
     while ($result = mysql_fetch_array($getresults)){
        if ($totalvotes!=0){
        $percentage = (round(($result["votes"]/$totalvotes)*10000))/100;
    }
        $imagewidth = round($percentage*2);
        echo $result["alternative"]." - $percentage% (".$result["votes"]." votes).
";
        echo "<img src=\"$imageid.gif\" width=\"$imagewidth\" height=\"10\" style=\"border:1px solid black\">

";
        $imageid++;
     }
     echo "
A total of $totalvotes votes has been submitted on this question.</font>";
}


if(!isset($submit) & !isset($results)) {
     ?>
     <form method="post" action="<? echo $_SERVER['PHP_SELF'] ?>" target="_blank">
     <font face="Verdana" size="2">
     <?

     $getquestion = mysql_query("select id,question from polls where active='yes' order by question limit 1");
     $question = mysql_fetch_row($getquestion);
     $pollid = $question[0];
     $dateactive = $question[1];
     $question = $question[1];
     echo "[b]$question[/b]

";
     $getalternatives = mysql_query("select id, alternative from poll_alternatives where poll_id='$pollid'");
     while ($writeit = mysql_fetch_array($getalternatives)){
           echo "<input type=\"radio\" name=polloption value=\"".$writeit["id"]."\"";
           if (!isset($checkedvar)){ echo "checked"; $checkedvar=1; }
           echo ">";
           echo " ".$writeit["alternative"]."
";
     }
     echo "<input type=\"hidden\" name=\"pollid\" value=\"$pollid\"></font>";
     echo "
<center><input type=\"Submit\" value=\"Vote\" name=\"submit\"";
     echo " style=\"background-color:white; color:black; font-family:Verdana; font-size:12px\">
";
   echo "<font face=\"Verdana\" size=\"1\"><a href=\"".$PHP_SELF."?results=1\" target=\"_blank\">View results</a></font>";
     echo "</center></form>";
 }
  
 elseif (isset($submit)){
     $checkforip = mysql_query("select ip from poll_ip where ip='$REMOTE_ADDR'");
     if (mysql_num_rows($checkforip)==0){
     mysql_query ("update poll_alternatives set votes=votes+1 where id='$polloption'");
     mysql_query ("update polls set votes=votes+1 where id='$pollid'");
     mysql_query ("insert into poll_ip (ip) values ('$REMOTE_ADDR')");
     echo "<font face=\"Verdana\" size=\"2\">Your vote has been counted.

</font>";
     }
     else { echo "<font face=\"Verdana\" size=\"2\">Only one vote per ip allowed.

</font>";}
     // skriva ut resultat
     writeresults();
  }

  elseif($results){
      writeresults();
  }  
     
 mysql_close($poll);
?>