PHP Manual: checkdate
checkdate
Description
bool checkdate ( int month, int day, int year )Checks the validity of the date formed by the arguments. A date is considered valid if each parameter is properly defined.
Parameters
monthThe month is between 1 and 12 inclusive.
dayThe day is within the allowed number of days for the given
month. Leapyears are taken into consideration.yearThe year is between 1 and 32767 inclusive.