Advanced PHP Captcha

PHP Captcha is an elegant, highly customizable, and secure captcha generator for PHP 8.0+. It supports advanced features like wave distortion, mathematical challenges, granular noise control, and custom font management.

Designed to be simple to use but powerful enough for any security requirement.

Requirements

• PHP 8.0 or higher
• GD Extension (ext-gd)

Features

• Highly Customizable: Control colors, fonts, noise, lines, and distortion.
• Math Mode: Present users with simple arithmetic verification (e.g., 5 + 3).
• Wave Distortion: Advanced warp algorithms to defeat OCR bots.
• Font Management: Use a specific font or randomize from a directory.
• Multiple Outputs: Stream directly to browser, get Base64, or save to disk.
• Zero Dependencies: Requires only standard PHP GD extension.

Installation

You can install the package via composer:

composer require olakunlevpn/phpcapcha

Basic Usage

Here is the quickest way to get a captcha up and running:

use Olakunlevpn\Captcha\Captcha;

session_start();

// Initialize
$captcha = new Captcha();

// Generate and Output an Image (200x70)
$captcha->create()->output();

// Store the code in session for validation later
$_SESSION['captcha_code'] = $captcha->getCode();

Advanced Usage

Customizing Appearance

You can chain methods to configure the captcha exactly how you want it.

use Olakunlevpn\Captcha\Captcha;

$captcha = new Captcha();

$captcha->setFont(__DIR__ . '/fonts/Monaco.ttf') // Or pass a directory for random font
        ->setTextColor(40, 40, 40)               // Dark Grey Text
        ->setBackgroundColor(240, 240, 240)      // Light Grey Background
        ->setLength(5)                           // 5 Characters
        ->setType('alpha')                       // Alphabetic only (no numbers)
        ->create(250, 80);                       // Create with specific dimensions

$captcha->output();

Math Challenge Mode

Instead of asking users to read distorted text, ask them to solve a simple math problem.

$captcha = new Captcha();

// Set type to 'math'
$captcha->setType('math');

$image = $captcha->create();

// The code will be the result (e.g., if image shows "5 + 3", code is "8")
$result = $captcha->getCode();

$captcha->output();

Granular Noise & Distortion Control

You have full control over the security elements.

$captcha = new Captcha();

// Enable/Disable specific elements
$captcha->setNoise(true, 100)      // Enabled, 100 dots
        ->setLines(true, 5)        // Enabled, 5 random lines
        ->setDistortion(true, 5, 40) // Enabled, Amplitude 5, Period 40
        ->create();

To create a Clean captcha (easier for humans, less secure against bots):

$captcha->setNoise(false)
        ->setLines(false)
        ->setDistortion(false)
        ->create();

Saving to File

Useful for caching or generating static assets.

$captcha->create();
$captcha->save(__DIR__ . '/captchas/image_123.png');

Inline Base64

Useful for passing the image directly to a view or API response without a separate endpoint.

$captcha->create();
$base64 = $captcha->getBase64();

echo '<img src="' . $base64 . '" />';

Validation

Validation is straightforward. Simply compare the user's input against the stored code.

session_start();

$input = $_POST['captcha']; // User input
$stored = $_SESSION['captcha_code']; // Stored from generation

// Use case-insensitive comparison for text
if (strtolower($input) === strtolower($stored)) {
    echo "Verification Successful!";
} else {
    echo "Incorrect Code.";
}

API Reference

Method	Description
setFont(string $path)	Path to a .ttf file OR a directory containing fonts (random selection).
setTextColor(int $r, int $g, int $b)	Sets the RGB color of the text.
setBackgroundColor(int $r, int $g, int $b)	Sets the RGB color of the background.
setLength(int $length)	Number of characters to generate (ignored in Math mode).
setType(string $type)	mixed (default), alpha, numeric, or math.
setNoise(bool $enable, int $count)	Toggle dots noise and set quantity.
setLines(bool $enable, int $count)	Toggle random lines and set quantity.
setDistortion(bool $enable, int $amp, int $period)	Toggle wave distortion. Amplitude/Period control wave shape.
create(int $width, int $height)	Generates the image resource. Must be called before output.
output()	Headers + Image binary stream (PNG).
getBase64()	Returns Base64 encoded string of the image.
save(string $path)	Saves the image to the specified file path.
getCode()	Returns the correct answer/code for validation.

Examples

Check the examples/ directory for full implementations:

• Vanilla CSS (examples/vanilla-css.php)
• Tailwind CSS (examples/tailwind.php)
• Bootstrap 5 (examples/bootstrap.php)
• jQuery/AJAX (examples/jquery.php)

AI assistant integration

This repository includes an AGENTS.md file specifically designed for AI assistants (like GitHub Copilot, Cursor, or Claude). If you're using an AI tool to help with your Laravel project:

• Point your AI assistant to the AGENTS.md file when asking about phpcapcha optimization.
• The file contains detailed guidance for analyzing components and determining eligibility.
• Use it for automated analysis - AI assistants can help audit your entire component library.

Example prompts for AI assistants:

• "Using the AGENTS.md file, analyze my components and tell me which can use phpcapcha"
• "Help me add phpcapcha to all eligible components following the guidelines"
• "Check if this component is safe for captcha protection based on AGENTS.md"

License

The MIT License (MIT). Please see License File for more information.