Sicherheitsbilder (Captchas) gegen SPAM  -  Die Klasse

<?php
 
/**
* Klasse zur Nutzung von Captchas
* @author Christian Blechert
* @since Septemper 2008
*
*/
 
class captcha {
   
   private $fontsize;
   private $fontfile;
   private $imagefile;
   private $align;
   
   function __construct($align="right") {
       $this->fontsize = 11; // Schriftgroesse
       $this->fontfile = "/captcha/VeraMono.ttf"; // absoluter Pfad zur Schriftfile
       $this->imagefile = "/captcha/captcha.png"; // absoluter Pfad zur Bilddatei
       $this->align = $align; // Ausrichtung
   }
   
// Token generieren
   function getToken() {
      $db = new mysql();
      $token = md5(time().mt_rand(0, 9999999));
      $db->mysqlQuery("insert into captcha_sessions set token='".$db->sqlij($token)."', ip='".$_SERVER['REMOTE_ADDR']."', dtime=NOW(), value='".md5(time())."'");
      return $token;
   }
   
// alte Tokens loeschen
   function deleteTokens() {
      $db = new mysql();
      $db->mysqlQuery("delete from captcha_sessions where dtime<FROM_UNIXTIME(".(time()-132000)).")");
   }
   
// Eingaben ueberpruefen
   function checkValue($value, $token) {
      $db = new mysql();
      $db->mysqlQuery("delete from captcha_sessions where token='".$db->sqlij($token)."' and value='".$db->sqlij($value)."' and ip='".$_SERVER['REMOTE_ADDR']."'");
      if($db->mysqlAffectedRows()<1) {
         return false;
      } else {
         return true;
      }
   }
   
// Captcha ausgeben
   function getCaptcha() {
      $this->deleteTokens();
      $token = $this->getToken();
      echo "<a class='captcha' href=\\\\"javascript:reloadImage('captcha');\\\\" title='Captcha neu laden'><img class='captcha' src='".REL_PATH."img/icons/reload.gif' alt='Captcha neu laden'></a> ";
      echo "<a class='captcha' href=\\\\"javascript:reloadImage('captcha');\\\\"><img id='captcha' class='captcha' src='".REL_PATH."etc/captcha/captcha.php?token=".$token."' alt='Captcha'></a>";
      echo "<input type='hidden' name='captcha_token' value='".$token."'>";
   }
   
// Bild generieren
   function getPicture($token) {
 
      $math[0] = " "; $math[1] = "-"; $math[2] = "*"; $math[3] = ":";
      $math = $math[mt_rand(0, sizeof($math)-1)];
      switch($math) {
         case " ": $wert1 = mt_rand(1, 20); $wert2 = mt_rand(1, 20);
                   $value = $wert1 $wert2; break;
         case "-": $wert1 = mt_rand(10, 99); $wert2 = mt_rand(0, 9);
                   $value = $wert1-$wert2; break;
         case "*": $wert1 = mt_rand(1, 5); $wert2 = mt_rand(1, 5);
                   $value = $wert1*$wert2; break;
         case ":": $wert2 = mt_rand(2, 9); $wert1 = mt_rand(2, 9);
                   $wert1 = $wert1*$wert2;
                   $value = $wert1/$wert2; break;
      }
      
      $db = new mysql();
      $result = $db->mysqlQuery("update captcha_sessions set value='".$db->sqlij($value)."' where token='".$db->sqlij($token)."' and ip='".$_SERVER['REMOTE_ADDR']."'");
      if($db->mysqlAffectedRows()<1) die("Unknown Token!");
 
      if($this->align=="left") {
         $text = "= ".$wert1." ".$math." ".$wert2;
      } else {
         $text = $wert1." ".$math." ".$wert2." =";
      }
 
      header('Content-type: image/png');
      $img = ImageCreateFromPNG($this->imagefile);
      $angle = rand(0,5);
      $t_x = mt_rand(0, 16);
      for($i=0; $i<strlen($text); $i  ) {
         $rgb[0] = mt_rand(0, 100);
         $rgb[1] = mt_rand(0, 255);
         $rgb[2] = mt_rand(0, 100);
 
         $t_y = mt_rand(13, 15);
         $color = ImageColorAllocate($img, $rgb[mt_rand(0, sizeof($rgb)-1)], $rgb[mt_rand(0, sizeof($rgb)-1)], $rgb[mt_rand(0, sizeof($rgb)-1)]); //Farbe
         imagettftext($img, $this->fontsize, $angle, $t_x, $t_y, $color, $this->fontfile, substr($text, $i, 1));
         if(substr($text, $i 1, 1)==" ") $t_x =2; else $t_x =10;
      }
      imagepng($img);
      imagedestroy($img);
   }
   
}