strtotime
strtotime — Parse about any English textual datetime description into a Unix timestampstrtotime( string $datetime, int|null $baseTimestamp = null ): int|falseThe function expects to be given a string containing an English date format and will try to parse that format into a Unix timestamp (the number of seconds since January 1 1970 00:00:00 UTC), relative to the timestamp given in baseTimestamp, or the current time if baseTimestamp is not supplied.
Warning: The Unix timestamp that this function returns does not contain information about time zones. In order to do calculations with date/time information, you should use the more capable DateTimeImmutable.
Each parameter of this function uses the default time zone unless a time zone is specified in that parameter. Be careful not to use different time zones in each parameter unless that is intended. See date_default_timezone_get() on the various ways to define the default time zoneParameters
Return Values
Returns a timestamp on success, false otherwise.More information about strtotime on official PHP documentation site