Auto-Translate WordPress Posts with GPT + WPML (Build Your Own Plugin)

Managing multilingual sites is hard. Writing the same post three times? Even harder. What if WordPress could auto-translate your posts into multiple languages the moment you hit “Publish”?
In this tutorial, we’ll build a WordPress plugin that connects WPML with GPT, automatically generating translated versions of your content.

✨ What You’ll Learn

How to create a custom WordPress plugin
How to hook into the save_post action
How to use WPML APIs to manage translations
How to integrate GPT for real-time translation

🔧 Step 1: Set Up the Plugin Skeleton
Inside wp-content/plugins/, create a folder:

auto-gpt-translator/

Inside it, add a file: auto-gpt-translator.php

<?php
/**
 * Plugin Name: Auto GPT Translator for WPML
 * Description: Automatically translates WordPress posts into multiple languages using GPT and WPML.
 * Version: 1.0
 * Author: Your Name
 */

if ( ! defined( 'ABSPATH' ) ) exit;

class AutoGPTTranslator {

    public function __construct() {
        add_action('save_post', [$this, 'auto_translate_post'], 20, 2);
    }

    public function auto_translate_post($post_id, $post) {
        if ( wp_is_post_revision($post_id) ) return;

        $languages = apply_filters('wpml_active_languages', NULL, ['skip_missing' => 0]);

        if (!$languages) return;

        foreach ($languages as $lang => $details) {
            if ($lang === apply_filters('wpml_default_language', NULL)) continue;

            $this->translate_and_save($post_id, $post, $lang);
        }
    }

    private function translate_and_save($post_id, $post, $lang) {
        $translated_content = $this->call_gpt_translation($post->post_content, $lang);
        $translated_title   = $this->call_gpt_translation($post->post_title, $lang);

        do_action('wpml_update_translated_post', [
            'element_id'    => $post_id,
            'trid'          => apply_filters('wpml_element_trid', NULL, $post_id, 'post_post'),
            'language_code' => $lang,
            'source_language_code' => apply_filters('wpml_default_language', NULL),
            'post_content'  => $translated_content,
            'post_title'    => $translated_title,
        ]);
    }

    private function call_gpt_translation($text, $target_lang) {
        $api_key = get_option('auto_gpt_api_key');
        if (!$api_key) return $text;

        $response = wp_remote_post("https://api.openai.com/v1/chat/completions", [
            'headers' => [
                'Content-Type' => 'application/json',
                'Authorization' => "Bearer $api_key",
            ],
            'body' => json_encode([
                'model' => 'gpt-4o-mini',
                'messages' => [
                    ['role' => 'system', 'content' => "Translate the following text into $target_lang."],
                    ['role' => 'user', 'content' => $text]
                ],
            ]),
        ]);

        if ( is_wp_error($response) ) return $text;

        $body = json_decode(wp_remote_retrieve_body($response), true);

        return $body['choices'][0]['message']['content'] ?? $text;
    }
}

new AutoGPTTranslator();

🔧 Step 2: Add a Settings Page
We need a simple admin page where you can paste your OpenAI API key.
Create settings.php inside the plugin folder:

<?php
add_action('admin_menu', function() {
    add_options_page(
        'Auto GPT Translator',
        'Auto GPT Translator',
        'manage_options',
        'auto-gpt-translator',
        'auto_gpt_translator_settings_page'
    );
});

add_action('admin_init', function() {
    register_setting('auto_gpt_translator_settings', 'auto_gpt_api_key');
});

function auto_gpt_translator_settings_page() {
?>
<div class="wrap">
    <h1>Auto GPT Translator Settings</h1>
    <form method="post" action="options.php">
        <?php settings_fields('auto_gpt_translator_settings'); ?>
        <?php do_settings_sections('auto_gpt_translator_settings'); ?>
        <table class="form-table">
            <tr valign="top">
                <th scope="row">OpenAI API Key</th>
                <td><input type="text" name="auto_gpt_api_key" value="<?php echo esc_attr(get_option('auto_gpt_api_key')); ?>" style="width: 400px;"/></td>
            </tr>
        </table>
        <?php submit_button(); ?>
    </form>
</div>
<?php
}

⚙️ Step 3: How It Works