Answers for "calculate end date from days and night in php"

php get start and end date of month and year

<?php

$query_date = '2010-02-04';

// First day of the month.
echo date('Y-m-01', strtotime($query_date));

// Last day of the month.
echo date('Y-m-t', strtotime($query_date));

calculate 18 years back date in php

date('Y-m-d', strtotime('18 years ago'))