PHP if & else statements

Are there any php coders out there that can help me with this? I am working on a chat network and i am trying to setup one of the parameters. On my chat network i have a list of official rooms that can be selected from a drop down box, or you can type in the name of a created chat room in to another field. On submitting this it forwards you to the chatrooom.php file and joins the appropriate room. This is my code

<PARAM name="Room" value="<? if (isset($_POST['created_room'])) <? echo $_POST['created_room'] ?>">

I need to add an else statement onto the end so that if someone just left the created_field blank it just looks at the official room list. Ive tried this code

<PARAM name="Room" value="<? if (isset($_POST['created_room'])) { echo $_POST['created_room']; } else { echo "$_POST['official_room']; } ?>"

but it doesnt seem to work. any ideas?

idk if you can make any sense of this post lol

 

nvm ive solved it now

 

You should really consider posting how you fixed it, since others would benefit from it.