What are best practices for structuring and formatting PHP code for form processing?

When processing forms in PHP, it is important to properly structure and format your code to ensure readability, maintainability, and security. One best practice is to separate your form processing logic from your HTML markup by using a separate PHP file for processing form submissions. Additionally, you should validate user input to prevent security vulnerabilities such as SQL injection or cross-site scripting attacks. Finally, consider using a PHP framework or library to streamline form processing and handle common tasks such as input validation and error handling.

<?php
// form-processing.php

// Check if form is submitted
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Validate form data
    $name = trim($_POST["name"]);
    $email = filter_var($_POST["email"], FILTER_VALIDATE_EMAIL);

    if (empty($name) || empty($email)) {
        // Handle form validation errors
        echo "Please fill out all required fields.";
    } else {
        // Process form data
        // Perform database operations, send email, etc.
        echo "Form submitted successfully!";
    }
}
?>