PHP Captcha Generator
Description
A PHP library for generating Captcha challenges using libgd., (*1)
Captcha examples
- Easy expression captcha:
- Hard expression captcha:
- Easy string captcha:
- Hard string captcha (colored):
Repositories
- GitHub: https://github.com/dangkyokhoang/PHP-Captcha-Generator.
- Packagist: https://packagist.org/packages/dkh/captcha-generator.
Required dependencies
- GD Graphics Library (ext-gd).
User Guide
Installation
You can easily get the library installed on your project by running this command.
composer require dkh/captcha-generator, (*2)
Implementation
Captcha types
-
ExpressionCaptcha expression captcha requires users to do basic arithmetic operations (addition, subtraction, multiplication and division) to solve.
-
StringCaptcha string captcha only requires users to recognize the characters in the string.
Create a captcha
To create a captcha, use new *Captcha($size?, $level?).
```php
// Default size: 3 and default difficulty level: 1
$expression_captcha = new ExpressionCaptcha();
$string_captcha = new StringCaptcha();, (*3)
// Specific size and difficulty level
$size = 10;
$level = 2;
$another_expression_captcha = new ExpressionCaptcha($size, $level);
```, (*4)
Get captcha's solved value
To get captcha's solved value, call $captcha->solve() or *Captcha::solveString($string).
Store the solved value somewhere, e.g in a session variable, to later verify user's captcha input.
```php
$_SESSION['captcha'] = $captcha->solve();, (*5)
// Or in a way that is infrequent,
// use static method Captcha::solveString()
$my_expression = '1+6:3-24';
$_SESSION['my_captcha'] = ExpressionCaptcha::solveString($my_expression);
```, (*6)
To verify user's captcha input, compare it with the captcha's previously solved value stored somewhere.
php
$user_captcha_input = $_POST['captcha'] ?? '';
$is_matched = $_SESSION['captcha'] === $user_captcha_input;, (*7)
Display the captcha image
To render captcha into image, call $captcha->render($options?), Captcha::renderString($string, $options?). Return value is a PNG image data string encoded with base64.
To dislay the captcha image, use data URL data:image/png;base64, or save the rendered image somewhere and return the image's path.
```php
$base64_image = $captcha->render();
echo sprintf('
', $base64_image);, (*8)
// Or in a way like this:
$my_string = 'any will do?';
$image_path = 'captcha.png';
$base64_image_to_be_saved = Captcha::renderString($my_string);
file_put_contents(
$image_path,
base64_decode($base64_image_to_be_saved)
);
echo sprintf('
', $image_path);, (*9)
// Image rendered with some options
$another_base64_image = $captcha->render([
'height' => 50,
'fill' => [0, 0, 0, 30],
// The alpha channel is optional
'color' => [255, 255, 255]
]);
echo sprintf(
'',
$another_base64_image
);
```, (*10)
Example implementation of the library
```php
<?php, (*11)
require_once 'vendor/autoload.php';, (*12)
use Dkh\ExpressionCaptcha;, (*13)
session_start();, (*14)
// Verify user's captcha input
if (isset($_POST['captcha']) && isset($_SESSION['captcha'])) {
$is_matched = $_POST['captcha'] === $_SESSION['captcha'];
} else {
$is_matched = null;
}
$message = $is_matched !== null ?
($is_matched ? 'Captcha matched' : 'Captcha not matched') :
'Try solving the captcha';, (*15)
// Create a captcha
$captcha = new ExpressionCaptcha();
// Store captcha's solved value
$_SESSION['captcha'] = $captcha->solve();
// Render the captcha into image
// The return value is a PNG image string encoded with base64
$base64_image = $captcha->render();, (*16)
echo sprintf(
'' .
'' .
', (*17)
' .
'
' .
', (*18)
Message: %s
' .
'' .
'',
$base64_image,
$message
);
```, (*19)
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