What are the key factors to consider in terms of security and performance when selecting a database class for a PHP web application with high database access requirements?

When selecting a database class for a PHP web application with high database access requirements, key factors to consider for security include parameterized queries to prevent SQL injection attacks, proper authentication and authorization mechanisms, and encryption of sensitive data. For performance, factors to consider include indexing of database tables, caching of frequently accessed data, and optimizing database queries.

// Example of using parameterized queries for security
$pdo = new PDO('mysql:host=localhost;dbname=mydatabase', 'username', 'password');
$stmt = $pdo->prepare('SELECT * FROM users WHERE username = :username');
$stmt->bindParam(':username', $username);
$stmt->execute();
$results = $stmt->fetchAll();