I'm not the PHP expert here (Raff should be around tomorrow to help answer) - but it seems what you're trying to do is create a new room. Are you getting any error back here? A couple of things - I think you need to log into the cocomo service, and here you're only supplying your account URL (no username and password). It also seems as though you need to supply a roomName, and optionally a template from which to build a room.
Anyhow, as I say, I'm not the expert, just trying to suggest some directions to try. Tomorrow, Raff should be able to be of more help.
The external authentication example for php shows you some real code, but it's specific to external authentication.
Also, for each language, php included, there is a "main" application (bottom of the script) that allow you to use the script as a standalone (commandline) application to manage your account, but it will also show how to use the different APIs.
In this particular case look at lines 613-614 for getting the CocomoAccount object and line 629 for room creation.
Hmmm, I just tried your example and it works for me (apart that you have an extra letter in the fist $pc_account - spelled $pc_acccount)
What version of PHP are you using ? I have developed and tested with PHP 5. Not sure if it would work in PHP 4 (for sure the error in line 35 is because PHP < 5 doesn't support 'const' - you could try to change it to a variable and see how far you get)