What are the potential pitfalls of saving form data in a text file using PHP?

One potential pitfall of saving form data in a text file using PHP is the lack of data validation, which can lead to security vulnerabilities and data corruption. To mitigate this risk, it is important to sanitize and validate the form data before saving it to the text file. Additionally, storing sensitive information in plain text files can expose it to unauthorized access.

// Sanitize and validate form data before saving to text file
$name = isset($_POST['name']) ? htmlspecialchars($_POST['name']) : '';
$email = isset($_POST['email']) ? filter_var($_POST['email'], FILTER_SANITIZE_EMAIL) : '';

// Save sanitized data to text file
$file = 'data.txt';
$data = "Name: $name\nEmail: $email\n";

file_put_contents($file, $data, FILE_APPEND);