Captcha tutorial in PHP
What is captcha?
An anti-spam form protection image written in PHP. For this captcha tutorial we need a form (plain html file), one PHP file which will generate a picture and a session and one PHP file which will check the result. Let's get started!
1. Form, a plain html file - test.html
First, we create a simple html file with a form inside and one field in it called check which would then be similar to this:
Code for this form inside a html file would be:
<img src="captcha.php"> <br>
<input type="text" size="10" name="check"> <br>
<input type="submit" name="submit" value="Submit">
</form>
We will save this file as test.html.
2. PHP file that creates a captcha - captcha.php
Now we will create a PHP file that creates an image/captcha and we will call it captcha.php. Source code for this file is:
<?php session_start();
$img = imagecreatefrompng('background.png');
$number = rand(100, 999);
$_SESSION['check'] = ($number);
$white = imagecolorallocate($img, 255, 255, 255);
imagestring($img, 10, 8, 3, $number, $white);
header ("Content-type: image/png"); imagepng($img);
?>
This code sets the random number between 100 and 999, assigns its value to the session called check and draws white numbers using 'background.png' for a background image. This creates our captcha. Background image is for example:
Now when we go to our test.html file it will look like this
3. PHP file that validates the captcha - checkit.php
This PHP file validates the user input. When user hits the Submit button, this file will check the captcha. Code:
<?php
session_start();
if(($_POST['check']) == $_SESSION['check']) {
echo 'Input OK';
}else{
echo 'Input Wrong';
}
?>
4. Download all files
We have prepared the files for download. Click here to download the whole package.
Rawn
Posted on 28. January 2010.
Hi and welcome to our site. More examples coming soon.