superglobal var names can't access object methods?

I am getting the following error message: Fatal error: Call to undefined function: add_folderfile() in /home/eprice/public_html/filerequest.php on line 756 I have the following code, line 756 is the line with the "if" test: // add the $ff_instance to the Print Request Folder using method add_folderfile() if (!$_SESSION['prfolder']->add_folderfile(serialize($ff_instance))) { die("Could not store \$ff_instance object in \$_SESSION['prfolder'] object"); } The add_folderfile() method of the $_SESSION['prfolder'] object looks like this: // add a folderfile to the Print Request Folder function add_folderfile($ff_obj) { $this->prf_folder[] = $ff_obj; return true; } And I have properly defined the class variable $this->prf_folder as an array at the top of the class in the following fasion: var $prf_folder = array(); The add_folderfile() function is defined as part of a class in an includefile called "classes.inc", which I know is being correctly included because every page on my site is built with a template class in that same file. Now that you've heard my life story... Does anyone know of any reasons why I might be getting the "undefined function" error? Am I unable to use a superglobal ($_SESSION['prfolder']) as the name of an object when attempting to use a method of that object (as in the code at the top of this email)? TIA, Erik ---- Erik Price Web Developer Temp Media Lab, H.H. Brown pricee@hhbrown.com