Problem mit spamschutz

<?php
 session_start();
        include "code1.php";
                          echo '<tr> 
                            <td><div align="center"><font color="#B5B5B5" size="1" face="Verdana, Arial, Helvetica, sans-serif"> 
                                Loui-Designs.de | Gästebuch</font></div></td>
                          </tr>
                        </table></td>
                      <td width="49"><img src="images/rmc.gif" width="49" height="36"></td>
                    </tr>
                  </table></td>
              </tr>
              <tr> 
                <td height="20" bgcolor="#5C5E4F" class="sideborders">';




include "mysql.php";






    if(!empty($_POST)) {
        @$z1 = intval($_POST['z1']);
        @$z2 = intval($_POST['z2']);
        @$gerechnet = intval($_POST['gerechnet']);
        $rechencheck = $z1 + $z2; 


      $check_ok =  ($gerechnet == $rechencheck && !empty($gerechnet) && !empty($rechencheck));
    }



  if(@$check_ok) {  
      $sql =  "INSERT INTO Gaestebuch
                 (Name, Email,Homepage, Inhalt, Datum)
               VALUES
                ('".$_POST['Name']."', '".$_POST['Email']."', '".$_POST['Homepage']."', '".$_POST['Inhalt']."', NOW())";
     $result = mysql_query($sql) OR die(mysql_error());
    }





    echo "               <h2>G&auml;stebuch</h2> ";


    if(empty($_GET['page']) == false)
      $page = $_GET['page'];
    else
      $page = '';
    echo '<form name="Formular" action="gbook.php?page='.$page.'" method="post">
            <table border="0"> 
                <tr>
                        <td><font face="Verdana" size="1" color="#008000">Dein Name : </td><td><input type="text" name="Name" maxlength="20" value="" /></td>
                </tr>
                <tr>                                                            

                        <td>Deine Email : </td><td><input type="text" name="Email" maxlength="40" value=""/></td>
                </tr>
                <tr>

                        <td>Deine Homepage : </td><td><input type="text" name="Homepage" maxlength="40" value=""/></td>
                </tr>

                <tr>
                        <td colspan="2">Dein Text (max. 500 Zeichen): <br />
                        <textarea name="Inhalt" rows="10" cols="40"></textarea>
                        </td>
                </tr>


                <tr>


                <td colspan="2">';


               $pageSize = 5;

                     $page = 1;
                     if(isset($_GET['page']))
                       $page = (int) $_GET['page'];

                    $sql = "SELECT Name FROM Gaestebuch";
                    $res  = mysql_query($sql);
                    $rows = mysql_num_rows($res);
                    //echo $rows;
                    $pages = ceil($rows/$pageSize);

                    $pLinks = '';

                    for($i=0; $i<$pages; $i++) {
                      $pLinks .= '<a href="/gbook.php?page='.$i.'">'.$i.'</a> ';
                    } 



     srand((double)microtime() * 1000000 );
        $zahl1 = rand(1, 9);
        $zahl2 = rand(1, 9); 

    echo "<input type='hidden' name='z1' value='$zahl1'> <input type='hidden' name='z2' value='$zahl2'>";
    echo "<strong>Sicherheitsabfrage</strong>";
    echo "Addiere $zahl1 + $zahl2 = <input type='text' name='gerechnet' size=2 maxlength=2>"; 



    if(@$check_ok) {
      echo "</br> Eintrag wurde hinzugefügt";
    }
    if(!empty($_POST) && !$check_ok) {
      echo "</br> Eintrag wurde nicht hinzugefügt";
    }
    echo "</br>";

    echo '<input type="submit" name="submit" value="Abschicken" />
                </td>
                </tr>

    </form></table>';

       echo '<a href="/login.php">Admin LogIn</a>'; 

   echo'    <hr />';


    echo 'Weitere Beitr&auml;ge: </br>';


    if(!empty($_GET['page']))
      echo '<a href="/gbuch.php?page='.($_GET['page']-1).'"> <-Zur&uuml;ck</a> &nbsp;';        


    echo $pLinks;

    if(!isset($_GET['page']))
      $page = 0;
    else
      $page = $_GET['page'];

    $sql = "SELECT
              Name,
              Email,
              Homepage,
              Inhalt,
              Datum
          FROM
              Gaestebuch
          ORDER BY
              Datum Desc 
          LIMIT ".(($page+1)*$pageSize).", ".$pageSize;

    $result = mysql_query($sql) OR die(mysql_error());

    $rows = mysql_num_rows($result);

    if(!empty($rows))
      echo '<font face="Verdana" size="1" color="#008000"><a href="/gbuch.php?page='.($page+1).'">Weiter></a>';



    echo "  <hr />  Sie befinden Sich auf Seite: &nbsp; ".($page);

    $sql = "SELECT
                Name,
                Email,
                Homepage,
                Inhalt,
                Datum
            FROM
                Gaestebuch
            ORDER BY
                Datum Desc 
            LIMIT ".($page*$pageSize).", ".$pageSize;
                $result = mysql_query($sql) OR die(mysql_error());

      if($n =mysql_num_rows($result)) {
        while($row = mysql_fetch_assoc($result)) {
            echo "<div class=\"newseintrag\">\n";
            echo "    <div class=\"Name\">\n";                                  //Ausgabe der Einträge der DB
            echo $row['Name'];
            echo "    </div>\n";
            echo "    <div class=\"Email\">\n";
            echo $row['Email'];
            echo "    </div>\n";
            echo "    <div class=\"Homepage\">\n";
            echo $row['Homepage'];
            echo "    </div>\n";
            echo "    <div class=\"Inhalt\">\n";
            echo nl2br($row['Inhalt']);                                         // \n in <br /> umwandeln
            echo "    </div>\n";
            echo "</div>\n";

           echo "<hr />";
        }
      }
 
   include "code2.php";

?>