What are some best practices for handling user input, such as passwords, in PHP to ensure data security and integrity?

When handling user input, especially sensitive data like passwords, it is crucial to ensure data security and integrity. One best practice is to always sanitize and validate user input to prevent SQL injection and cross-site scripting attacks. Additionally, passwords should never be stored in plain text; instead, they should be hashed using a strong cryptographic algorithm like bcrypt.

// Sanitize and validate user input
$username = filter_var($_POST['username'], FILTER_SANITIZE_STRING);
$password = filter_var($_POST['password'], FILTER_SANITIZE_STRING);

// Hash the password using bcrypt
$hashed_password = password_hash($password, PASSWORD_DEFAULT);

// Store the username and hashed password in the database
// Example SQL query: INSERT INTO users (username, password) VALUES ('$username', '$hashed_password');