php form with auth.net

Hey guys I'm having a hell of a time trying to setup a order form that would post to auth.net and place the charge on it then if it could not place the charge on it would say "sorry your card has be denied please use another one" type of error else it would show a thank you receipt page.

My question is is there a class/script that would make this task easier I basicly want to do this

auth->fname($FNAME) //First name of customer
auth->lname($LNAME) // lastname
..
.(and so on)
.
auth->creditcard($CCNUMBER) //Number of the card

if(auth->runtransaction==successful){
echo 'transaction is good';
}
else{
echo "card denied";
}

any help would be great

//Edit Forgot to mention its for subscription billing