if php page loaded into div, show or hide HTML

I've basically got a checkout page (index.php) in which I load 4 other pages into the "content div" (when the link is pressed)

<div id="content"></div>

using..

 $("#content").load(link + '.php');

The problem is im using two different paypal checkout forms (standard and recurring) on the same page (index.php) which both have conflicting ID's which I cannot change.

So it looks like..

<form id="checkout_form" name="_xclick" action="http://ift.tt/1f0qRSq" id="form" method="post" >
        <input type="hidden" id="unique" name="cmd" value="_xclick" />

</form>

and the second one..

<form id="checkout_form2" name="_xclick" action="http://ift.tt/1f0qRSq" id="form" method="post" >
            <input type="hidden" id="unique" name="cmd" value="_xclick" />

    </form>

I'd like to basicaly write a function that says.. IF page ID inside content div =xyz then use/show form1 else if page=zzz use/show form2

..the issue is basically causing empty fields to sometimes be sent through to the paypal IPN