Syntax of checkdate
bool checkdate(int month, int day, int year)
Returns true if the month, date, and year as given in the parameters are valid (Gregorian), and false if not. A date is considered valid if the year falls between 1 and 32,767 inclusive, the month is between 1 and 12 inclusive, and the day is within the number of days the specified month has (including leap years)
Example of checkdate
<?php
var_dump(checkdate(12, 31, 2000));
var_dump(checkdate(2, 29, 2001));
?>
bool(true) bool(false)