This guide provides the necessary steps to implement the YouTube to MP4 conversion function directly into your WordPress theme.

1. The Conversion Function (manus-youtube-converter.php)

The provided PHP code implements a shortcode that displays a form. When a user submits a YouTube URL, the function calls the Cobalt API (a free, open-source API for media conversion) to process the video and returns a direct download link for the MP4 file.

Key Features:

• API Used: Cobalt API (using a public instance: https://co.wuk.sh/).
• Method: Uses WordPress’s built-in wp_remote_post function for secure HTTP requests.
• Output: The shortcode renders a simple form and, upon successful submission, redirects the user to the MP4 download link.

2. Implementation Steps

You have two primary options for adding this code to your WordPress site:

Option A: Adding to the Theme’s functions.php (Recommended by User)

This is the fastest way to implement the function, as requested.

1. Access Your Theme Files: Connect to your WordPress site via FTP or use your hosting provider’s File Manager.
2. Navigate to Theme Directory: Go to wp-content/themes/your-theme-name/.
3. Edit functions.php: Open the functions.php file for editing.
4. Add the Code: Paste the entire content of the provided manus-youtube-converter.php file at the very end of your functions.php file, just before the closing ?> tag (if one exists).

Option B: Creating a Simple Plugin (Recommended for Best Practice)

Creating a small plugin is generally safer and ensures the function remains active even if you change your theme.

1. Create a New Directory: In wp-content/plugins/, create a new folder named manus-youtube-converter.
2. Create the Plugin File: Inside the new folder, create a file named manus-youtube-converter.php.
3. Add Plugin Header: Paste the following header at the top of the file: <?php /** * Plugin Name: Manus YouTube to MP4 Converter * Description: Adds a shortcode to convert YouTube videos to MP4 using the Cobalt API. * Version: 1.0 * Author: Manus AI */ // [PASTE THE REST OF THE CODE HERE]
4. Add the Code: Paste the entire content of the provided manus-youtube-converter.php file immediately after the plugin header.
5. Activate Plugin: Log in to your WordPress admin dashboard, go to Plugins, and activate the Manus YouTube to MP4 Converter plugin.

3. Usage

Once the code is implemented, you can use the shortcode on any page or post:

Action	Shortcode
Insert Converter Form	[youtube_to_mp4_converter]

1. Create a New Page/Post: Go to your WordPress editor.
2. Add Shortcode Block: Insert a Shortcode block (or a Custom HTML block) into the content.
3. Paste the Shortcode: Enter [youtube_to_mp4_converter].
4. Publish: Save and publish the page. The form will now be visible on your site.

4. Important Considerations

Aspect	Detail
API Stability	The Cobalt API is a community-driven, open-source project. While generally reliable, public instances can be unstable, rate-limited, or shut down without notice. For high-volume or mission-critical use, consider hosting your own Cobalt instance or using a paid, commercial API [1].
Legal/ToS	Downloading content from YouTube may violate their Terms of Service. Ensure your use case complies with all applicable laws and YouTube’s policies.
Server Requirements	The code uses wp_remote_post, which requires the cURL library to be enabled on your PHP installation (standard on most hosts).

References

[1] Cobalt API Documentation: Methods, acceptable values, headers, responses and everything else related to making and parsing requests from a cobalt api instance. [https://github.com/imputnet/cobalt/blob/main/docs/api.md]

<?php
/**
 * YouTube to MP4 Converter Functionality
 *
 * This file contains the necessary PHP functions to create a shortcode
 * for converting YouTube videos to MP4 format using the Cobalt API.
 *
 * Usage: [youtube_to_mp4_converter]
 *
 * IMPORTANT: This code should be added to your theme's functions.php file
 * or included as a custom plugin.
 */

// 1. Core function to call the Cobalt API
function manus_cobalt_convert_video($youtube_url) {
    // The Cobalt API endpoint (using a known public instance)
    // NOTE: Public instances can be unstable or rate-limited. For production,
    // it is recommended to host your own instance or use a paid API.
    $api_url = 'https://co.wuk.sh/'; 

    // Prepare the request body
    $body = array(
        'url' => $youtube_url,
        'videoQuality' => 'max', // Request the highest quality available
        'youtubeVideoContainer' => 'mp4' // Explicitly request MP4 container
    );

    // Prepare the arguments for wp_remote_post
    $args = array(
        'body'    => json_encode($body),
        'headers' => array(
            'Content-Type' => 'application/json',
            'Accept'       => 'application/json',
        ),
        'timeout' => 30, // Set a reasonable timeout for the conversion process
        'sslverify' => false // Set to true in a production environment with proper SSL
    );

    // Make the POST request using WordPress's HTTP API
    if (!function_exists('wp_remote_post')) {
        // Fallback for environments where WordPress functions are not loaded (should not happen in functions.php)
        return array('error' => 'WordPress HTTP functions not available.');
    }
    
    $response = wp_remote_post($api_url, $args);

    // Check for WordPress HTTP errors
    if (is_wp_error($response)) {
        return array('error' => 'API Request Error: ' . $response->get_error_message());
    }

    $response_code = wp_remote_retrieve_response_code($response);
    $response_body = wp_remote_retrieve_body($response);
    $data = json_decode($response_body, true);

    // Check for API errors or unexpected response
    if ($response_code !== 200 || !isset($data['status'])) {
        $error_message = isset($data['error']) ? $data['error'] : 'Unknown API error.';
        return array('error' => "Conversion failed. Status Code: {$response_code}. Message: {$error_message}");
    }

    // Handle successful response
    if ($data['status'] === 'tunnel' || $data['status'] === 'redirect') {
        return array(
            'success' => true,
            'download_url' => $data['url'],
            'filename' => $data['filename']
        );
    } elseif ($data['status'] === 'error') {
        $error_code = isset($data['error']['code']) ? $data['error']['code'] : 'Unknown';
        return array('error' => "Cobalt API Error: {$error_code}. Please check the URL and try again.");
    } else {
        // Handle other statuses like 'picker' or 'local-processing' if necessary, 
        // but for a simple downloader, we'll treat them as an error for now.
        return array('error' => "Conversion status '{$data['status']}' not supported for direct download.");
    }
}

// 2. Shortcode function to display the form and handle submission
function manus_youtube_downloader_shortcode() {
    // Check if the form has been submitted
    if (isset($_POST['manus_convert_submit']) && isset($_POST['youtube_url'])) {
        // Sanitize the input URL
        $youtube_url = esc_url_raw(trim($_POST['youtube_url']));

        if (!empty($youtube_url)) {
            // Call the conversion function
            $result = manus_cobalt_convert_video($youtube_url);

            if (isset($result['success']) && $result['success']) {
                // Redirect the user to the download URL
                // This is the most reliable way to initiate a download from an external service.
                wp_redirect($result['download_url']);
                exit;
            } else {
                // Display error message
                $error_message = $result['error'];
                $output = '<div style="color: red; border: 1px solid red; padding: 10px; margin-bottom: 15px;">Error: ' . esc_html($error_message) . '</div>';
            }
        } else {
            $output = '<div style="color: orange; border: 1px solid orange; padding: 10px; margin-bottom: 15px;">Please enter a valid YouTube URL.</div>';
        }
    }

    // Output the form
    $output .= '
        <div class="manus-youtube-converter-wrapper" style="max-width: 600px; margin: 20px auto; padding: 20px; border: 1px solid #ccc; border-radius: 5px;">
            <h3 style="margin-top: 0;">YouTube to MP4 Converter</h3>
            <form method="post" action="' . esc_url($_SERVER['REQUEST_URI']) . '">
                <p>
                    <label for="youtube_url" style="display: block; margin-bottom: 5px; font-weight: bold;">Enter YouTube Video URL:</label>
                    <input type="url" id="youtube_url" name="youtube_url" placeholder="e.g., https://www.youtube.com/watch?v=dQw4w9WgXcQ" required 
                           style="width: 100%; padding: 10px; box-sizing: border-box; border: 1px solid #ddd; border-radius: 3px;">
                </p>
                <p>
                    <input type="submit" name="manus_convert_submit" value="Convert & Download MP4" 
                           style="background-color: #ff0000; color: white; padding: 10px 15px; border: none; border-radius: 3px; cursor: pointer; font-weight: bold;">
                </p>
                <p style="font-size: 0.8em; color: #666;">
                    * This service uses a third-party API (Cobalt) for conversion.
                </p>
            </form>
        </div>
    ';

    return $output;
}

// 3. Register the shortcode
add_shortcode('youtube_to_mp4_converter', 'manus_youtube_downloader_shortcode');

// Optional: Ensure wp_remote_post is available if this file is loaded early
if (!function_exists('wp_remote_post')) {
    require_once(ABSPATH . 'wp-includes/pluggable.php');
    require_once(ABSPATH . 'wp-includes/http.php');
}