What are the best practices for handling form submission in PHP, especially when dealing with dropdown lists?

When handling form submissions in PHP, especially when dealing with dropdown lists, it is important to validate the input data to prevent security vulnerabilities such as SQL injection. One best practice is to use prepared statements when interacting with a database to safely insert user input. Additionally, properly sanitizing and validating the input data before processing it can help prevent errors and ensure the data is in the correct format.

// Assuming a form with a dropdown list named 'dropdown_list' is submitted
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Validate and sanitize the input data
    $selected_option = isset($_POST['dropdown_list']) ? $_POST['dropdown_list'] : '';
    
    // Use prepared statements to insert data into the database
    $stmt = $pdo->prepare("INSERT INTO table_name (column_name) VALUES (:selected_option)");
    $stmt->bindParam(':selected_option', $selected_option);
    $stmt->execute();
}