I'm not the sharpest knife around but I'd think you could:
$person1 = 'there@address.com';
$person2 ='there2@address.com';
$subject = 'Blah';
$message = 'Blah Blah';
mail($person1, $subject, $message);
mail($person2, $subject, $message);
Correct me if I'm wrong. Although Weedpacket's way is probaly better, personally I never caught on to that BCC thing :o