Membuat Capcha dengan PHP

Pertama buat file php dengan nama captcha.php.

<?php
session_start();
$text = rand(10000,99999);
$_SESSION["vercode"] = $text;
$height = 25;
$width = 65; 

$image_p = imagecreate($width, $height);
$black = imagecolorallocate($image_p, 0, 0, 0);
$white = imagecolorallocate($image_p, 255, 255, 255);
$font_size = 14; 

imagestring($image_p, $font_size, 5, 5, $text, $white);
imagejpeg($image_p, null, 80);
?>
buat file htmk dengan nama test.html
<form action="submit.php" method="post">
Comment: <textarea name="coment"></textarea><br> 
Enter Code <img src="captcha.php"><input type="text" name="vercode" /><br>
<input type="submit" name="Submit" value="Submit" />
</form> 

Buat file php dengan nama submit.php
<?php
session_start();
if ($_POST["vercode"] != $_SESSION["vercode"] OR $_SESSION["vercode"]=='')  {
     echo  '<strong>Incorrect verification code.</strong><br>';
} else {
     // add form data processing code here
     echo  '<strong>Verification successful.</strong><br>';
};
?> 

Sumber : http://www.phpjabbers.com/captcha-image-verification-php19.html