What is the difference between PHP and HTML in the context of the issue described in the forum thread?

Issue: The forum thread discusses a problem where users are unable to submit a form due to missing input validation. The solution involves using PHP to validate the form inputs before processing the data. PHP provides server-side validation capabilities, allowing developers to check the user input before submitting the form. Unlike HTML, which is a markup language used for creating the structure of web pages, PHP can handle dynamic content generation and data processing. By incorporating PHP validation logic, developers can ensure that the form data is secure and accurate before further processing.

<?php
// Check if form is submitted
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Validate form inputs
    $name = $_POST['name'];
    $email = $_POST['email'];
    
    // Check if name is not empty
    if (empty($name)) {
        echo "Name is required";
    }
    
    // Check if email is a valid email address
    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        echo "Invalid email format";
    }
    
    // Process form data if validation passes
    // Additional logic here
}
?>