What are some best practices for form validation and error handling in PHP?

One best practice for form validation in PHP is to use server-side validation in addition to client-side validation to ensure data integrity and security. Error handling should also be implemented to provide clear and informative messages to users when validation fails.

// Form validation example
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $name = $_POST["name"];
    
    // Server-side validation
    if (empty($name)) {
        $error = "Name is required";
    }
    
    // Error handling
    if (isset($error)) {
        echo $error;
    } else {
        // Process form data
    }
}