Description
this functionality allows to check is it human or webbot. It's made by giving to visitor task simple for human and very hard for webbot - perfect solution is OCR (Optical Character Recognition).

Example
Click on image to change the code.

HTML code <form method=post name=captcha> <img src="captcha.php" onclick="document.location.href='?change=1';" style="cursor:pointer;" title="Click to change code."> <input type=text name="captcha"> <input type=submit value="Check"> </form> <b><key:result></b>
PHP code if(!$_SESSION[captcha] || $_GET[change]) $_SESSION[captcha]=rand(100000,999999); if($_GET[change]) redirect($page); if($_POST[captcha]){ if($_POST[captcha]==$_SESSION[captcha]){ $t->replace("result","Yes, code is correct!"); }else{ $t->replace("result","No, code is wrong!"); } }