How can PHP developers ensure that the access code validation process does not interfere with the functionality of the website or online shop when using cookies or .htaccess protection?

When implementing access code validation using cookies or .htaccess protection in PHP, developers can ensure that it does not interfere with the website's functionality by carefully testing the validation process and ensuring that it does not disrupt the normal flow of the website or online shop. Additionally, developers should handle any errors or exceptions gracefully to prevent any issues that may arise from the validation process.

// Example of access code validation using cookies
if(isset($_COOKIE['access_code'])) {
    $access_code = $_COOKIE['access_code'];
    
    // Validate access code here
    if($access_code !== 'valid_code') {
        // Redirect or display error message
        header('Location: error_page.php');
        exit;
    }
} else {
    // Redirect or display error message
    header('Location: error_page.php');
    exit;
}