Php - 代码在月后消失

I have a code which displays hint for users, f.e.

echo "Please read a new rulebook";

And is there a way in php to add code which will delete this hint after a month (so I will not have to delete it manually myself?) ?

Code: (replace "SomeDate" with the current time, like Aug 4 2016 15:04:00)

if(strtotime("now")<strtotime("SomeDate +1month")) echo "Please read a new rulebook";