Class Constructor (PDO __construct)

When creating your own library for working with a database, the constructor (the __construct method) is the part of the code that does the most important work behind the scenes. Its main task is to execute automatically as soon as you create a new object of your class. Instead of writing connection code in each file separately, the constructor does it for you – it prepares the DSN string, checks the credentials, and establishes a secure PDO connection, which is then ready to be used throughout the entire application.

EXAMPLE

<?php
class Database {
    private $server = "localhost";
    private $username = "root";
    private $password = "";
    private $db_name = "pdo_db";
    public $connection;

    // The constructor runs automatically upon "new Database()"
    public function __construct() {
        $this->connection = null;

        try {
            // Added charset=utf8mb4 for character support
            $dsn = "mysql:host=" . $this->server . ";dbname=" . $this->db_name . ";charset=utf8mb4";
            $this->connection = new PDO($dsn, $this->username, $this->password);
            $this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            echo "Library: Connection successfully established via constructor!";
        } catch(PDOException $e) {
            echo "Library Error: " . $e->getMessage();
        }
    }
}

// Usage:
$myDatabase = new Database(); 
?>

RESULT

The result will be displayed here...

By doing this, we ensure that we do not have to write connection code in every single file. We set up the class once, and then we just use it. Any potential connection errors are caught inside the class, which keeps our main code clean.

The constructor is defined using the reserved name __construct.
The connection is stored in a public property of the class so it can be accessed where needed.
Using a class allows us to use the same connection throughout the entire application.