HELP -> Setting forward date stamp

[trafix]

ok i use

PHP Code:

$endmonitor= strtotime("now +365 days"); 


to set a date stamp 1 year for now

question....

how do i set add to a future datestamp

ummm ..... say a user has x to expire in 10 days ... and he wants to extend that for anouther 40 days

what code do i need to add 40 days to the original 10 days making it a total of 50 days before x expires?

is that too confusing...i hope not