How can functions be used to improve flexibility and readability in PHP scripts, especially when dealing with form validation and output?

Using functions in PHP scripts can improve flexibility and readability by allowing you to encapsulate reusable code blocks and logic. When dealing with form validation and output, creating separate functions for validation and output can make your code easier to manage and understand. This modular approach also makes it easier to make changes or updates to your validation and output processes without affecting the rest of your script.

// Function for form validation
function validateForm($formData) {
    // Validation logic here
    // Return true if validation passes, false otherwise
}

// Function for output
function displayOutput($data) {
    // Output formatting logic here
    // Echo or return the formatted output
}

// Example usage
$formData = $_POST;
if (validateForm($formData)) {
    $outputData = processData($formData);
    displayOutput($outputData);
} else {
    echo "Form validation failed.";
}