Lesson 17 — Databases

Connecting to MySQL with PDO

PDO (PHP Data Objects) provides a consistent, secure interface for connecting PHP to a MySQL database and running queries against it.

Establishing a Connection

A PDO connection requires a Data Source Name (DSN) describing the database driver, host, and database name, along with credentials. Wrapping the connection in try/catch handles failures gracefully.

PHP — Connecting with PDO 
try {
    $pdo = new PDO(
        "mysql:host=localhost;dbname=school_db;charset=utf8mb4",
        "root",
        ""
    );
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
    die("Connection failed: " . $e->getMessage());
}

Common Mistakes

  • Hardcoding database credentials directly in a file that might be committed to version control or exposed accidentally.
  • Forgetting to set PDO::ATTR_ERRMODE to ERRMODE_EXCEPTION, missing helpful error details when something goes wrong.
  • Not specifying a charset in the DSN, which can cause issues with special characters and emoji.
  • Using the older mysqli or mysql_* functions in new code when PDO offers a more consistent, driver-agnostic interface.

Professional Tip

Store database credentials in environment variables or a configuration file kept outside version control, rather than hardcoding them directly in your PHP scripts.

Your Turn

Set up a local MySQL database and write a PHP script that establishes a PDO connection to it, printing a success message if the connection works and a clear error otherwise.

Mini Quiz

What does PDO stand for in PHP?