mktime

mktime is a commonly used function name in programming libraries for converting a broken-down time into a numeric timestamp. In the C standard library, the function prototype is time_t mktime(struct tm *tm); In PHP, mktime(hour, minute, second, month, day, year, is_dst) returns a Unix timestamp for a date in the local timezone.

In the C form, the function accepts a pointer to a struct tm that contains fields for tm_sec, tm_min, tm_hour, tm_mday, tm_mon, tm_year, and auxiliary fields tm_wday, tm_yday, tm_isdst. mktime normalizes fields that are out of range, adjusting the date and time as needed. It also fills in tm_wday and tm_yday and returns the corresponding time_t value that represents the local time. The operation is influenced by the process's time zone and DST settings; if the given time cannot be represented, or if the normalization fails, mktime returns (time_t) -1.

In PHP, mktime constructs a timestamp based on the provided date and time components in the server's local timezone. All parameters are optional and default to the current local time when omitted. The final parameter is_dst can be used to force daylight saving time handling or set to -1 to have PHP determine DST automatically. The function returns an integer timestamp on success, or false on failure. The PHP equivalent in UTC is gmmktime.