I have table which has the table field name:
- Start Date
- Duration Count (e.g. 1, 2 or 3)
- Duration Name (e.g. Daily, Monthly, Yearly)
- End Date

How do I code in PHP to calculate the end date from a particular start date?

E.g. The start date is on 1st January 2013, and duration count is 1, duration name is yearly.
Which actually meant to be 1 year duration. How do I code in order to get the answer of
31st December 2013 in my end date column?

Example Formula: $StartDate + $DurationCount & $DurationName = $EndDate?

Noticed that I'm facing the problem when it comes to monthly issues. For example is an invoice bill
starts on 31st January 2013, after one month the bill supposed to be due in March. It matters when
whether 2013 is a lear year or non leap year.