config.php

<?php
define('DB_HOST', 'localhost'); 
define('DB_USER', 'root');
define('DB_PASS', '');
define('DB_NAME', 'project_management_system');

// define('DB_HOST', 'localhost'); 
// define('DB_USER', 'Vignesh_G');
// define('DB_PASS', 'Vigneshg091002');
// define('DB_NAME', 'PMS');

class Database {
    private static $instance = null;
    private $conn;
    
    private function __construct() {
        try {
            $this->conn = new mysqli(DB_HOST, DB_USER, DB_PASS, DB_NAME);
            if ($this->conn->connect_error) {
                die("Connection failed: " . $this->conn->connect_error);
            }
            $this->conn->set_charset("utf8mb4");
        } catch (Exception $e) {
            die("Database connection error: " . $e->getMessage());
        }
    }
    
    public static function getInstance() {
        if (self::$instance === null) {
            self::$instance = new Database();
        }
        return self::$instance;
    }
    
    public function getConnection() {
        return $this->conn;
    }
    
    public function query($sql) {
        return $this->conn->query($sql);
    }
    
    public function prepare($sql) {
        return $this->conn->prepare($sql);
    }
    
    public function escape($string) {
        return $this->conn->real_escape_string($string);
    }
    
    public function lastInsertId() {
        return $this->conn->insert_id;
    }
}

function getDB() {
    return Database::getInstance()->getConnection();
}
?>