PHP 8 Singleton PostgreSQL Database Connection

gistfile1.txt

<?php

class Database {
    private static ?Database $instance = null;
    private ?resource $connection = null;
    private string $host;
    private string $dbname;
    private string $user;
    private string $password;

    // Private constructor to prevent instantiation
    private function __construct(string $host, string $dbname, string $user, string $password) {
        $this->host = $host;
        $this->dbname = $dbname;
        $this->user = $user;
        $this->password = $password;
        
        $this->connect();
    }

    // Private clone method to prevent cloning
    private function __clone() {}

    // Private unserialize method to prevent unserialization
    private function __wakeup() {}

    // Create the connection to the PostgreSQL database
    private function connect(): void {
        $connectionString = "host={$this->host} dbname={$this->dbname} user={$this->user} password={$this->password}";
        $this->connection = pg_connect($connectionString);

        if (!$this->connection) {
            throw new Exception("Connection failed: " . pg_last_error());
        }
    }

    // Get the instance of the Database Singleton
    public static function getInstance(string $host, string $dbname, string $user, string $password): Database {
        if (self::$instance === null) {
            self::$instance = new Database($host, $dbname, $user, $password);
        }

        return self::$instance;
    }

    // Return the current database connection
    public function getConnection(): ?resource {
        return $this->connection;
    }

    // Close the connection
    public function closeConnection(): void {
        if ($this->connection) {
            pg_close($this->connection);
            $this->connection = null;
        }
    }
}

// Example usage code follows...

// Set your PostgreSQL database credentials
$host = 'localhost';
$dbname = 'your_database';
$user = 'your_user';
$password = 'your_password';

try {
    // Get the Singleton instance and get the connection
    $db = Database::getInstance($host, $dbname, $user, $password);
    $connection = $db->getConnection();

    // Use the connection to execute queries
    $result = pg_query($connection, "SELECT * FROM users");

    if ($result) {
        while ($row = pg_fetch_assoc($result)) {
            echo "ID: " . $row['id'] . " - Name: " . $row['name'] . "<br>";
        }
    } else {
        echo "Error: " . pg_last_error($connection);
    }

    // Optionally close the connection
    $db->closeConnection();

} catch (Exception $e) {
    echo "Error: " . $e->getMessage();
}
?>