CKEditor::textarea method not available

Hello,
I've downloaded CKEditor 3.6.3 and in the ckeditor.php file in editors root are folowing lines:

 Create CKEditor class instance and use one of available methods to insert CKEditor.
<?php
   $CKEditor = new CKEditor();
   echo $CKEditor->textarea("field1", "<p>Initial value.</p>");
?>

My attempt to do this resulted in this error:

Call to undefined method CKEditor::textarea() in blah blah blah 

(note that the error reports missing method, not class so i HAVE included the appropriate file before calling)

So whats wrong? I want to output ckeditor via PHP not assign it to textarea after page is loaded for performance reasons.