<?php
  session_start();
  $captcha = substr(str_shuffle("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"),0,4);
  $_SESSION['captcha'] = $captcha;

  $gambar = imagecreate(100,100);
  $wk=imagecolorallocate($gambar,255,222,173);
  $wt=imagecolorallocate($gambar,0,0,0);
  $rand = rand(1,60);
  imagefilledrectangle($gambar,0,0,50,20,$wk);
  imagestring($gambar,10,$rand,$rand,$captcha,$wt);
  imagejpeg($gambar);
 ?>