What are some best practices for handling form validation in PHP to prevent submitting empty fields?

When handling form validation in PHP to prevent submitting empty fields, one best practice is to check if the required fields are not empty before processing the form submission. This can be done by using conditional statements to validate each input field individually. Additionally, displaying error messages to prompt users to fill in the required fields can help improve the user experience.

// Check if form is submitted
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Check if required fields are not empty
    if (!empty($_POST['field1']) && !empty($_POST['field2'])) {
        // Process form submission
        // Additional validation and processing code here
    } else {
        // Display error message for empty fields
        echo "Please fill in all required fields.";
    }
}