Membuat Memory Percakapan AI Agent PHP

<?php

class SessionMemory
{
    private string $sessionKey;

    public function __construct(string $sessionKey = 'chat_history')
    {
        $this->sessionKey = $sessionKey;
        if (session_status() === PHP_SESSION_NONE) {
            session_start();
        }
    }

    public function add(string $role, string $content): void
    {
        if (!isset($_SESSION[$this->sessionKey])) {
            $_SESSION[$this->sessionKey] = [];
        }
        $_SESSION[$this->sessionKey][] = [
            'role'    => $role,
            'content' => $content,
        ];
    }

    public function getAll(): array
    {
        return $_SESSION[$this->sessionKey] ?? [];
    }

    public function clear(): void
    {
        $_SESSION[$this->sessionKey] = [];
    }

    public function getLastN(int $n): array
    {
        $history = $this->getAll();
        return array_slice($history, -$n);
    }
}

-- Migration: Tabel chat_sessions
CREATE TABLE IF NOT EXISTS chat_sessions (
    id          BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    session_id  VARCHAR(128) NOT NULL,
    user_id     BIGINT UNSIGNED NULL,
    created_at  DATETIME DEFAULT CURRENT_TIMESTAMP,
    updated_at  DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    INDEX idx_session_id (session_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

-- Migration: Tabel chat_messages
CREATE TABLE IF NOT EXISTS chat_messages (
    id          BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    session_id  VARCHAR(128) NOT NULL,
    role        ENUM('system','user','assistant','tool') NOT NULL,
    content     LONGTEXT NOT NULL,
    tool_name   VARCHAR(100) NULL,
    token_count INT NULL,
    created_at  DATETIME DEFAULT CURRENT_TIMESTAMP,
    INDEX idx_session_id (session_id),
    INDEX idx_created_at (created_at)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

<?php

class DatabaseMemory
{
    private PDO $pdo;
    private string $sessionId;

    public function __construct(PDO $pdo, string $sessionId)
    {
        $this->pdo       = $pdo;
        $this->sessionId = $sessionId;
    }

    public function add(string $role, string $content, ?string $toolName = null): void
    {
        $stmt = $this->pdo->prepare(
            'INSERT INTO chat_messages (session_id, role, content, tool_name) VALUES (?, ?, ?, ?)'
        );
        $stmt->execute([$this->sessionId, $role, $content, $toolName]);
    }

    public function getAll(int $limit = 50): array
    {
        $stmt = $this->pdo->prepare(
            'SELECT role, content FROM chat_messages
             WHERE session_id = ?
             ORDER BY created_at ASC
             LIMIT ?'
        );
        $stmt->execute([$this->sessionId, $limit]);
        return $stmt->fetchAll(PDO::FETCH_ASSOC);
    }
}

// Strategi: Selalu sertakan system prompt + N pesan terakhir
public function buildContextMessages(array $history, string $systemPrompt, int $maxMessages = 20): array
{
    $messages = [['role' => 'system', 'content' => $systemPrompt]];
    $recentHistory = array_slice($history, -$maxMessages);
    return array_merge($messages, $recentHistory);
}

<?php

// Generate Vector Embedding untuk Semantic Memory
function createEmbedding(string $text, string $apiKey): array
{
    $ch = curl_init('https://api.openai.com/v1/embeddings');
    curl_setopt_array($ch, [
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_POST           => true,
        CURLOPT_POSTFIELDS     => json_encode([
            'model' => 'text-embedding-3-small',
            'input' => $text,
        ]),
        CURLOPT_HTTPHEADER     => [
            'Content-Type: application/json',
            'Authorization: Bearer ' . $apiKey,
        ],
    ]);

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

    $data = json_decode($response, true);
    return $data['data'][0]['embedding'] ?? []; // Larik float vector (1536 dimensi)
}