What are some best practices for handling form input data in PHP to avoid errors like the one described in the thread?

The issue described in the thread is likely related to not properly sanitizing and validating form input data in PHP, which can lead to errors or security vulnerabilities. To avoid this, it is recommended to always use functions like `htmlspecialchars()` and `mysqli_real_escape_string()` to sanitize user input and validate input data using functions like `filter_var()`.

// Example of sanitizing and validating form input data in PHP
$name = htmlspecialchars($_POST['name']);
$email = filter_var($_POST['email'], FILTER_VALIDATE_EMAIL);
$message = htmlspecialchars($_POST['message']);

// Use mysqli_real_escape_string() for database queries
$escaped_name = mysqli_real_escape_string($conn, $name);
$escaped_email = mysqli_real_escape_string($conn, $email);
$escaped_message = mysqli_real_escape_string($conn, $message);