比较并检查PHP Date（）

Question

I'm trying to figure out how to compare against date() . I'm following along in a tutorial about how to use this function to compare the current time against the time a cache file was last modified. In the tutorial, the author uses "10800" as 3 hours and the code looks something like:

(filemtime($cache) < (time()-10800))

I have no problem understanding how this comparison works but I just don't get how the the expression of time, "10800" , is formatted.

Just for the record I spent a solid 15 minutes looking for an answer so I'm not just being ignorant of Google haha.

Thanks!

Answer 1

10800 is in seconds..

all unix timestamps are measured in seconds since the epoch... 1 being the first second of 1970.

This explains why when you have a bad strtotime value and you are interpreting it with date ie

date(strtotime("last tomorrowday"));

it ends up showing you 1969-12-31 ... strtotime is returning 0 and if 1 is the first second of 1970 then 0 will be interpreted as the last second of 1969

Answer 2

It's in seconds,

3 hours = 3 * 60 * 60 = 10800 seconds

As time function returns the current time measured in the number of seconds since the Unix Epoch (January 1 1970 00:00:00 GMT). You neeed to subtract 10800 from it to get timestamp of time before 3 hours .