Building Reusable Database Connection Factories

A connection factory centralizes DSN construction and safe PDO options.

The examples focus on the operation itself, including the important distinction: A factory returns PDO instances; repositories perform queries with them.

What It Does

Use the examples below to observe the behavior on a small dataset before extending it to application code.

Before You Start

The examples use PHP 8.2+ features where shown. Database snippets require the corresponding PDO driver, demo tables, and credentials configured outside source code.

Example 1: Basic Use

The factory centralizes PDO initialization and takes credentials from server-side configuration.

<?php
final class PdoFactory {
    public static function mysql(string $dsn, string $user, string $password): PDO {
        return new PDO($dsn, $user, $password, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
    }
}
$dsn = "mysql:host=127.0.0.1;dbname=demo;charset=utf8mb4";
$pdo = PdoFactory::mysql($dsn, getenv("DB_USER") ?: "app", getenv("DB_PASSWORD") ?: "");
echo $pdo->getAttribute(PDO::ATTR_DRIVER_NAME);

This example is meant for a configured application environment; output depends on the installed extension, external service, or database contents.

Example 2: Checking Behavior

The factory centralizes PDO initialization and takes credentials from server-side configuration. A caller can use the same factory for configuration checks and queries.

<?php
final class PdoFactory {
    public static function mysql(string $dsn, string $user, string $password): PDO {
        return new PDO($dsn, $user, $password, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
    }
}
$dsn = "mysql:host=127.0.0.1;dbname=demo;charset=utf8mb4";
$pdo = PdoFactory::mysql($dsn, getenv("DB_USER") ?: "app", getenv("DB_PASSWORD") ?: "");
echo $pdo->getAttribute(PDO::ATTR_ERRMODE);

This example is meant for a configured application environment; output depends on the installed extension, external service, or database contents.

Example 3: Practical Example

The factory centralizes PDO initialization and takes credentials from server-side configuration. A caller can use the same factory for configuration checks and queries.

<?php
final class PdoFactory {
    public static function mysql(string $dsn, string $user, string $password): PDO {
        return new PDO($dsn, $user, $password, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
    }
}
$dsn = "mysql:host=127.0.0.1;dbname=demo;charset=utf8mb4";
$pdo = PdoFactory::mysql($dsn, getenv("DB_USER") ?: "app", getenv("DB_PASSWORD") ?: "");
echo $pdo->query("SELECT 1")->fetchColumn();

This example is meant for a configured application environment; output depends on the installed extension, external service, or database contents.

Important Behavior and Edge Cases

Credentials should come from environment or a secret store, not source control.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• A connection factory centralizes DSN construction and safe PDO options.
• Credentials should come from environment or a secret store, not source control.
• A factory returns PDO instances; repositories perform queries with them.

Use Building Reusable Database Connection Factories when its documented behavior matches the problem. Test the relevant edge cases in your own runtime before deploying it.