AI Category Recommendation System for Drupal 11 Using PHP and OpenAI

In Drupal, choosing the right category for a page or article is very important. However, in real life, people can make mistakes. Editors may pick the wrong category, use different categories for similar content, or publish posts quickly without giving much thought to categorization.

AI-powered Drupal 11 can now recommend the best category for a node. Instead of depending only on keywords, this recommendation is based on the node's actual content.

You will learn how to create a custom Drupal 11 module by following this tutorial. After using OpenAI's capabilities to analyze node content, the module will intelligently suggest or assign the best taxonomy term.

This fits in perfectly with our AI + PHP CMS series, where we're adding modern AI features to improve traditional CMS workflows.

What This Module Will Do

Our AI category system will:

• Analyze node body content on save
• Compare it against existing taxonomy terms
• Recommend the most relevant category
• Automatically assign it (or display it to editors)

Use cases include:

• Blog posts
• Documentation pages
• News articles
• Knowledge bases

Prerequisites

Make sure you have:

• Drupal 11
• PHP 8.1+
• Composer
• A taxonomy vocabulary (example: categories)
• An OpenAI API key

Step 1: Create the Custom Module

Create a new folder:

    
        /modules/custom/ai_category/
    

Inside it, create the below files:

• ai_category.info.yml
• ai_category.module

ai_category.info.yml

    
        name: AI Category Recommendation
        type: module
        description: Automatically recommend and assign taxonomy categories using AI.
        core_version_requirement: ^11
        package: Custom
        version: 1.0.0
    

Step 2: Hook Into Node Save

We’ll use hook_entity_presave() to analyze content before it’s stored.

ai_category.module

    
        use Drupal\Core\Entity\EntityInterface;
        use Drupal\taxonomy\Entity\Term;

        /**
        * Implements hook_entity_presave().
        */
        function ai_category_entity_presave(EntityInterface $entity) {
            if ($entity->getEntityTypeId() !== 'node') {
                return;
            }

            // Only apply to articles (adjust as needed)
            if ($entity->bundle() !== 'article') {
                return;
            }

            $body = $entity->get('body')->value ?? '';
            if (empty($body)) {
                return;
            }

            $category = ai_category_recommend_term($body);
            if ($category) {
                $entity->set('field_category', ['target_id' => $category]);
            }
        }
    

This ensures our logic runs only for specific content types and avoids unnecessary processing.

Step 3: Ask AI for Category Recommendation

We’ll send the node content plus a list of available categories to OpenAI and ask it to pick the best one.

    
        function ai_category_recommend_term(string $text): ?int {
            $apiKey = 'YOUR_OPENAI_API_KEY';
            $endpoint = 'https://api.openai.com/v1/chat/completions';

            $terms = \Drupal::entityTypeManager()
                ->getStorage('taxonomy_term')
                ->loadTree('categories');

            $categoryNames = array_map(fn($t) => $t->name, $terms);

            $prompt = "Choose the best category from this list:\n"
                    . implode(', ', $categoryNames)
                    . "\n\nContent:\n"
                    . strip_tags($text)
                    . "\n\nReturn only the category name.";

            $payload = [
                "model" => "gpt-4o-mini",
                "messages" => [
                ["role" => "system", "content" => "You are a content classification assistant."],
                ["role" => "user", "content" => $prompt]
                ],
                "temperature" => 0
            ];

            $ch = curl_init($endpoint);
            curl_setopt_array($ch, [
                CURLOPT_RETURNTRANSFER => true,
                CURLOPT_HTTPHEADER => [
                "Content-Type: application/json",
                "Authorization: Bearer {$apiKey}"
                ],
                CURLOPT_POST => true,
                CURLOPT_POSTFIELDS => json_encode($payload),
                CURLOPT_TIMEOUT => 15
            ]);

            $response = curl_exec($ch);
            curl_close($ch);

            $data = json_decode($response, true);
            $chosen = trim($data['choices'][0]['message']['content'] ?? '');

            foreach ($terms as $term) {
                if (strcasecmp($term->name, $chosen) === 0) {
                return $term->tid;
                }
            }

            return null;
        }
    

What’s happening here:

• Drupal loads all available categories
• AI receives both content + allowed categories
• AI returns one matching category name
• Drupal maps it back to a taxonomy term ID

Step 4: Enable the Module

• Place the module in /modules/custom/ai_category
• Go to Extend → Enable module
• Enable AI Category Recommendation
• That’s it — no UI needed yet.

Step 5: Test It

• Create a new Article
• Write content related to PHP, Drupal, AI, or CMS topics
• Click Save
• The Category field is auto-filled

Example:

Article content:

        “This tutorial explains how to build a custom Drupal 11 module using PHP hooks…”
    

AI-selected category:

    
        Drupal
    

Optional Enhancements

Once the basics work, you can extend this system:

• Show AI recommendation as a suggestion, not auto-assignment
• Add admin settings (API key, confidence threshold)
• Use Queue API for bulk classification
• Switch to embeddings for higher accuracy
• Log category confidence scores
• Support multi-term assignment

Security & Performance Tips

• Never hard-code API keys (use settings.php or environment variables)
• Limit text length before sending to AI
• Cache recommendations to reduce API calls
• Add fallbacks if the AI response is invalid

Next up, we’ll build a AI Duplicate Content Detector for Symfony.