In what scenarios should developers avoid mixing PDO with MySQLi in PHP code to prevent errors and ensure consistency in database interactions?

Developers should avoid mixing PDO with MySQLi in PHP code to prevent errors and ensure consistency in database interactions. Mixing these two database extensions can lead to confusion, inconsistencies, and potential errors in the codebase. It is recommended to choose one database extension and stick with it throughout the project for better maintainability and readability.

// Example of using only PDO for all database interactions

try {
    $pdo = new PDO("mysql:host=localhost;dbname=mydatabase", "username", "password");
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // Perform database operations using PDO
    $stmt = $pdo->prepare("SELECT * FROM users");
    $stmt->execute();
    $users = $stmt->fetchAll(PDO::FETCH_ASSOC);

    // Close the database connection
    $pdo = null;
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}