#php Make captcha image simple

<?php
ob_start();
session_start();
 header("Content-type: image/jpeg");
 $im = imagecreate(120,25);
 $white = imagecolorallocate($im, 16,17,32);
 $black = imagecolorallocate($im, 255,255,255);
 $randcode = rand(10000,99999);
 $_SESSION['captcha']=$randcode;

 imagettftext($im, 16, 0, 11, 22, $black, "./fonts/04b_09__.ttf",  $_SESSION['captcha'] );
 imagepng($im);
 imagedestroy($im);
?>