I keep getting the following error and I do not know why:

Warning: call_user_func_array() expects parameter 1 to be a valid callback, first array member is not a valid class name or object in views_php_plugin_wrapper->__call() (line 43 of /../sites/all/modules/views_php/plugins/views/views_php_plugin_wrapper.inc).

I had a site on a different server which was working perfectly. I rebuilt the site from the ground up on the new server and now I get this error any time I view a page that has views_php being used. Strangely enough the content displays just fine.