Problem with "FCKeditorAPI", How I do it´s work ?

Hi, I´m use the FCK Editor with PHP in my project, but, I get some errors response in the browser FF and IE .

the error is : FCKeditorAPI is not defined.

but, I declared a instance of object, inside the PHP script like this:

$oFCKeditor = new FCKeditor('instanceName') ;
 $oFCKeditor->BasePath   = TEXT_EDITOR_PATH;
 $oFCKeditor->Create();