Simple Image Captcha

//the form <form action="file.php" method="post" > <input type="text" id="name" name="name" placeholder="Name" /> <input type="text" id="email" name="email" placeholder="Email" /> <!-- CAPTCHA --> <label for="CaptchaTxt"><img src="captcha.php" alt="Captcha Code" /></label> <input type="text" name="CaptchaTxt" id="CaptchaTxt" placeholder="Enter the code above"/> <!-- CAPTCHA --> <button type="submit"></button> </form> //captcha.php <?php session_start(); $alphanum = "arjaysonbarantez1234567890"; // generate the verication code $random = substr(str_shuffle($alphanum), 0, 4); // create the hash for the random number and put it in the session $_SESSION['img_code_val'] = md5($random); // create the image $image = imagecreate(45, 18); // use white as the background image $bgColor = imagecolorallocate ($image, 246, 241, 230); // the text color is black $textColor = imagecolorallocate ($image, 0, 0, 0); // write the random number imagestring ($image, 5, 5, 1, $random, $textColor); // send several headers to make sure the image is not cached // taken directly from the PHP Manual // Date in the past header("Expires: Mon, 09 Dec 1900 04:00:00 GMT"); // always modified header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT"); // HTTP/1.1 header("Cache-Control: no-store, no-cache, must-revalidate"); header("Cache-Control: post-check=0, pre-check=0", false); // HTTP/1.0 header("Pragma: no-cache"); // send the content type header so the image is displayed properly header('Content-type: image/jpeg'); // send the image to the browser imagejpeg($image); // destroy the image to free up the memory imagedestroy($image); ?> // file.php <?php session_start(); ?> <?php if ($_SESSION['img_code_val'] != md5($_POST['CaptchaTxt'])) { $validcaptcha = 0; } else { error_reporting(E_ALL ^ E_NOTICE); $validcaptcha = 1; <?php if ($validcaptcha == 1) { // do somenthing } else { // do something else } ?>