Simple If Statement

[Opteron]

i'm trying to say: if term starts with aa then use function new. i tried following unsuccesfully:

if(ereg("^aa", $term)) {
$new...
}

and

if(term == "^aa") {
$new...
}

but they didnt work out. what is the correct way of saying this?

[Weedpacket]

if(substr($term,0,2)=='aa')
{
....
}