README

Description

A PHP library for generating Captcha challenges using libgd.

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

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?).

// Default size: 3 and default difficulty level: 1
$expression_captcha = new ExpressionCaptcha();
$string_captcha = new StringCaptcha();

// Specific size and difficulty level
$size = 10;
$level = 2;
$another_expression_captcha = new ExpressionCaptcha($size, $level);

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.

$_SESSION['captcha'] = $captcha->solve();

// Or in a way that is infrequent,
// use static method *Captcha::solveString()
$my_expression = '1+6:3-2*4';
$_SESSION['my_captcha'] = ExpressionCaptcha::solveString($my_expression);

Verify user's captcha input

To verify user's captcha input, compare it with the captcha's previously solved value stored somewhere.

$user_captcha_input = $_POST['captcha'] ?? '';
$is_matched = $_SESSION['captcha'] === $user_captcha_input;

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.

$base64_image = $captcha->render();
echo sprintf('<img src="data:image/png;base64,%s">', $base64_image);

// 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('<img src="/%s">', $image_path);

// 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(
    '<img src="data:image/png;base64,%s">',
    $another_base64_image
);

Example implementation of the library

<?php

require_once 'vendor/autoload.php';

use Dkh\ExpressionCaptcha;

session_start();

// 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';

// 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();

echo sprintf(
    '<!DOCTYPE html>' .
    '<html>' .
    '<body>' .
    '<form method="POST">' .
    '<img src="data:image/png;base64,%s"><br>' .
    '<input name="captcha" placeholder="Input captcha">' .
    '<input type="submit" value="Submit"><br>' .
    '</form>' .
    '<div>Message: %s</div>' .
    '</body>' .
    '</html>',
    $base64_image,
    $message
);

dkh / captcha-generator

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