What are some common security measures that should be implemented when using PHP for VPN authentication?

Issue: When using PHP for VPN authentication, it is crucial to implement strong security measures to protect sensitive user data and prevent unauthorized access. Some common security measures include using secure hashing algorithms for passwords, implementing SSL/TLS encryption for data transmission, and validating user input to prevent SQL injection attacks. Code snippet:

// Use a secure hashing algorithm like bcrypt for storing passwords
$hashed_password = password_hash($password, PASSWORD_BCRYPT);

// Implement SSL/TLS encryption for secure data transmission
// Example: enable SSL/TLS in PHP configuration
// Note: SSL/TLS should also be configured on the server

// Validate user input to prevent SQL injection attacks
$username = mysqli_real_escape_string($conn, $_POST['username']);
$password = mysqli_real_escape_string($conn, $_POST['password']);