A small neat PHP Captcha Script

I cannot stand the way some Captcha scripts look and work. Personally I give up very quickly when signing onto a web-service if I cannot 'identify' the Captcha characters easily. making hard for spider-bots is one thing, but making it impossible for humans is quite another.

So, here is a simple, clear captcha script written in PHP that makes it harder for bots to submit your forms, but obviously it not impenetrable (I would presume).

I have called it 'Matcha' to differentate it from other Captcha scripts (at least for us BlueBox-ers).

Invoke the Matcha session string at the top of your form like this:

• $_SESSION["matcha"]=strtoupper(chr(65+rand(0,25)).chr(65+rand(0,25)).chr(65+rand(0,25)).chr(65+rand(0,25)).chr(65+rand(0,25)));
• This will create a string of 5 uppercase A-Z characters.

In your form add these 2 rows to the layout:

• <div class=cr_form_label>
  Characters to Match:
  </div>
  <div>
  <img src=\"<!--:class:bb_mymodule:matcha:-->\" >
  </div>
  
  <div class=cr_form_label>
  Enter Characters*:
  </div>
  <div>
  <input class=cr_form_field id=matcha name=global[matcha]>
  </div>
• Remember to create a new BlueBox2.0 module called bb_mymodule (use the module name here, not this example name)

In the PHP BlueBox2.0 module (bb_mymodule) create a function as follows:

• function matcha($err){
          global $global;
          $im = @imagecreatetruecolor(257, 36);
          $text_color = imagecolorallocate($im, 140, 140, 140);
          $white = imagecolorallocate($im, 255, 255, 255);
          imagefilledrectangle($im, 0, 0, 257, 36, $white);
          $font_file = 'portal/database_name/custom_modules/captcha.ttf';
          imagefttext($im, 15, 3, 70, 30, $text_color, $font_file, $_SESSION["matcha"]);
          imagepng($im,"portal/database_name/custom_modules/c/$_SESSION[matcha].jpg");
          imagedestroy($im);
          resp("portal/database_name/custom_modules/c/$_SESSION[matcha].jpg?".uniqid());
      }
• You will need to upload a TTF font to the server that is suitably difficult to read for a bot-scanner.

 Finally, do a check when your form gets posted, to see if the entered amount matches the Matcha string:

• if(strtoupper($global[matcha])!=$_SESSION[matcha]){
       resp("The characters you have entered do no match the string shown.");
       return;
  }