Gästebuch Captcha Fehler

<?php
   session_start();
   unset($_SESSION['captcha_spam']);


   function randomString($len) {
      function make_seed(){
         list($usec , $sec) = explode (' ', microtime());
         return (float) $sec + ((float) $usec * 100000);
      }
      srand(make_seed());


      //Der String $possible enthält alle Zeichen, die verwendet werden sollen
      $possible="ABCDEFGHJKLMNPRSTUVWXYZabcdefghijkmnpqrstuvwxyz23456789";
      $str="";
      while(strlen($str)<$len) {
        $str.=substr($possible,(rand()%(strlen($possible))),1);
      }
   return($str);
   }


   $text = randomString(5);  //Die Zahl bestimmt die Anzahl stellen
   $_SESSION['captcha_spam'] = $text;


   header('Content-type: image/png');
   $img = ImageCreateFromPNG('/captcha/captcha.PNG'); //Backgroundimage
   $color = ImageColorAllocate($img, 0, 0, 0); //Farbe
   $ttf = $_SERVER['DOCUMENT_ROOT']."/captcha/XFILES.TTF"; //Schriftart
   $ttfsize = 25; //Schriftgrösse
   $angle = rand(0,5);
   $t_x = rand(5,30);
   $t_y = 35;
   imagettftext($img, $ttfsize, $angle, $t_x, $t_y, $color, $ttf, $text);
   imagepng($img);
   imagedestroy($img);
?>

<?php
echo '
<form action="" method="post">
<table>
<tr><td>Name:</td><td> <input type="text" name="username"></td></tr>
<tr><td>Email:</td><td> <input type="text" name="email"></td></tr>
<tr><td>Homepage:</td><td> <input type="text" name="homepage"></td></tr>
<tr><td colspan="2">Nachricht:


<textarea name="nachricht" cols="35" rows="8"></textarea><td></tr>
<tr><td>[img]captcha/captcha.php[/img]</td>
<td><input type="text" name="sicherheitscode" size="5"></td></tr>
<tr><td colspan="2"><input type="submit" value="Eintragen" name="senden"></td></tr>
</table>
</form>
';
IF(isset($_POST["senden"])){
include('datenbank.php');
$username = $_POST["username"];
$email = $_POST["email"];
$homepage = $_POST["homepage"];
$nachricht = $_POST["nachricht"];
$zeit = time();
$code = "INSERT INTO gbuch (id, username, email, homepage, nachricht, zeit, ip) VALUES('','$username','$email','$homepage','$nachricht','$zeit','$REMOTE_ADDR')";
session_start();
if(isset($_SESSION['captcha_spam']) AND $_POST["sicherheitscode"] ==
$_SESSION['captcha_spam']){
unset($_SESSION['captcha_spam']);
}else{
   die ("Der Sicherheitscode ist falsch!");
}
$eintragen = mysql_query($code);
IF($eintragen){
echo 'Eintrag hinzugefuegt';
}
}
?>

<?php
session_start();
if(isset($_SESSION['captcha_spam']) AND $_POST["sicherheitscode"] == $_SESSION['captcha_spam']){
unset($_SESSION['captcha_spam']);
IF(isset($_POST["senden"])){
include('datenbank.php');
$username = $_POST["username"];
$email = $_POST["email"];
$homepage = $_POST["homepage"];
$nachricht = $_POST["nachricht"];
$zeit = time();
$code = "INSERT INTO gbuch (id, username, email, homepage, nachricht, zeit, ip) VALUES('','$username','$email','$homepage','$nachricht','$zeit','$REMOTE_ADDR')";
$eintragen = mysql_query($code);
IF($eintragen){
echo 'Eintrag hinzugefuegt';
}
}
session_start();
if(isset($_SESSION['captcha_spam']) AND $_POST["sicherheitscode"] == $_SESSION['captcha_spam']){
unset($_SESSION['captcha_spam']);
?>

<?php
   session_start();
   unset($_SESSION['captcha_spam']);


   function randomString($len) {
      function make_seed(){
         list($usec , $sec) = explode (' ', microtime());
         return (float) $sec + ((float) $usec * 100000);
      }
      srand(make_seed());


      //Der String $possible enthält alle Zeichen, die verwendet werden sollen
      $possible="ABCDEFGHJKLMNPRSTUVWXYZabcdefghijkmnpqrstuvwxyz23456789";
      $str="";
      while(strlen($str)<$len) {
        $str.=substr($possible,(rand()%(strlen($possible))),1);
      }
   return($str);
   }


   $text = randomString(5);  //Die Zahl bestimmt die Anzahl stellen
   $_SESSION['captcha_spam'] = $text;


   header('Content-type: image/gif');
   $img = ImageCreateFromGIF('captcha.GIF'); //Backgroundimage
   $color = ImageColorAllocate($img, f, f, f); //Farbe
   $ttf = $_SERVER['DOCUMENT_ROOT']."captcha//XFILES.TTF"; //Schriftart
   $ttfsize = 25; //Schriftgrösse
   $angle = rand(0,5);
   $t_x = rand(5,30);
   $t_y = 35;
   imagettftext($img, $ttfsize, $angle, $t_x, $t_y, $color, $ttf, $text);
   imagegif($img);
   imagedestroy($img);
?>