db.php

<?php
/**
 * SQLite integration for WordPress
 * This file enables WordPress to use SQLite database instead of MySQL
 */

// Prevent direct access
if (!defined('ABSPATH')) {
    exit;
}

// Check if SQLite extension is available
if (!extension_loaded('pdo_sqlite')) {
    wp_die('SQLite PDO extension is not available. Please install php-sqlite3.');
}

// Define SQLite database path
if (!defined('DB_FILE')) {
    define('DB_FILE', ABSPATH . 'wp-content/database/wordpress.db');
}

// Create database directory if it doesn't exist
$db_dir = dirname(DB_FILE);
if (!file_exists($db_dir)) {
    wp_mkdir_p($db_dir);
}

/**
 * Custom database class for SQLite
 */
class SQLite_DB {
    private $pdo;
    private $last_error = '';
    private $last_insert_id = 0;
    private $num_rows = 0;
    
    public function __construct() {
        $this->connect();
    }
    
    private function connect() {
        try {
            $this->pdo = new PDO('sqlite:' . DB_FILE);
            $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            $this->pdo->exec('PRAGMA foreign_keys = ON');
        } catch (PDOException $e) {
            $this->last_error = $e->getMessage();
            wp_die('Database connection failed: ' . $this->last_error);
        }
    }
    
    public function query($sql) {
        try {
            // Convert MySQL syntax to SQLite
            $sql = $this->mysql_to_sqlite($sql);
            
            $stmt = $this->pdo->prepare($sql);
            $result = $stmt->execute();
            
            if ($result) {
                $this->last_insert_id = $this->pdo->lastInsertId();
                $this->num_rows = $stmt->rowCount();
                return $stmt;
            }
            
            return false;
        } catch (PDOException $e) {
            $this->last_error = $e->getMessage();
            return false;
        }
    }
    
    private function mysql_to_sqlite($sql) {
        // Basic MySQL to SQLite conversion
        $sql = str_replace('`', '"', $sql);
        $sql = preg_replace('/AUTO_INCREMENT/i', 'AUTOINCREMENT', $sql);
        $sql = preg_replace('/INT\(\d+\)/i', 'INTEGER', $sql);
        $sql = preg_replace('/TINYINT\(\d+\)/i', 'INTEGER', $sql);
        $sql = preg_replace('/BIGINT\(\d+\)/i', 'INTEGER', $sql);
        $sql = preg_replace('/VARCHAR\((\d+)\)/i', 'TEXT', $sql);
        $sql = preg_replace('/LONGTEXT/i', 'TEXT', $sql);
        $sql = preg_replace('/DATETIME/i', 'TEXT', $sql);
        $sql = preg_replace('/TIMESTAMP/i', 'TEXT', $sql);
        
        return $sql;
    }
    
    public function get_results($sql, $output = OBJECT) {
        $stmt = $this->query($sql);
        if (!$stmt) return null;
        
        $results = [];
        while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
            if ($output === OBJECT) {
                $results[] = (object) $row;
            } else {
                $results[] = $row;
            }
        }
        
        return $results;
    }
    
    public function get_row($sql, $output = OBJECT) {
        $stmt = $this->query($sql);
        if (!$stmt) return null;
        
        $row = $stmt->fetch(PDO::FETCH_ASSOC);
        if (!$row) return null;
        
        if ($output === OBJECT) {
            return (object) $row;
        }
        
        return $row;
    }
    
    public function get_var($sql) {
        $stmt = $this->query($sql);
        if (!$stmt) return null;
        
        $row = $stmt->fetch(PDO::FETCH_NUM);
        return $row ? $row[0] : null;
    }
    
    public function insert_id() {
        return $this->last_insert_id;
    }
    
    public function last_error() {
        return $this->last_error;
    }
    
    public function num_rows() {
        return $this->num_rows;
    }
}

// Initialize SQLite database connection
$wpdb = new SQLite_DB();

// WordPress database compatibility
if (!isset($GLOBALS['wpdb'])) {
    $GLOBALS['wpdb'] = $wpdb;
}