What is the best way to determine an expiration date based on a previous selection in PHP?

To determine an expiration date based on a previous selection in PHP, you can use the strtotime() function to add a specific time interval to the selected date. For example, if the user selects a date in a form, you can add a certain number of days to that date to calculate the expiration date. This can be achieved by taking the selected date as input, converting it to a timestamp using strtotime(), adding the desired number of days, and then formatting the result as a date.

// Get the selected date from the form
$selectedDate = $_POST['selected_date'];

// Define the number of days for expiration
$expirationDays = 30;

// Calculate the expiration date by adding the number of days to the selected date
$expirationDate = date('Y-m-d', strtotime($selectedDate . ' + ' . $expirationDays . ' days'));

// Output the expiration date
echo "Expiration Date: " . $expirationDate;