Can't use function DateAdd

[linda_says]

I get a Fatal error: Call to undefined function: dateadd().

my script:
$today = date("m.d.y");
$duration= DateAdd ("m",3,$today);

$today return me "07.02.02"

How come I cannot use the function DateAdd?

[tomkleijkers]

Function DateAdd() doesn't exists in php. What do you want to do? (Check manual, DateAdd() isn't in it.)