why must you divide by 31556952 like if you don't you get a big number but where did someone come up with that number?
$ctime - $ctime() alone returns the number of seconds between now and when you were born. You first divide it by 60 to return minutes (since there's 60 seconds in a minute), and again by 60 (since there's 60 minutes in an hour), then 24, then 365.25. So you'll get
($ctime - $ctime()) /60/60/24/365

Since all that is the same thing as:
($ctime - $ctime()) /(606024*365)

since (606024*365) = 31557600 (which I guess is mIRC's estimate of 31556952)

you can simplify it to
($ctime - $ctime()) / 31556952