What are the best practices for handling form data in PHP, specifically when using the $_POST variable?

When handling form data in PHP using the $_POST variable, it is important to sanitize and validate the data to prevent security vulnerabilities such as SQL injection and cross-site scripting attacks. One common practice is to use functions like htmlspecialchars() to sanitize user input before processing it. Additionally, it is recommended to validate the data against expected formats and values to ensure data integrity.

// Sanitize and validate form data
$name = isset($_POST['name']) ? htmlspecialchars($_POST['name']) : '';
$email = isset($_POST['email']) ? filter_var($_POST['email'], FILTER_VALIDATE_EMAIL) : '';
$message = isset($_POST['message']) ? htmlspecialchars($_POST['message']) : '';

// Validate email format
if (!$email) {
    echo "Invalid email address";
    // Handle error or redirect back to form
} else {
    // Process form data
    // ...
}