In what situations can the class be directly referenced without require or include?

Under what circumstances can a class be directly referenced without require or include ??? PHPcode/** loading configuration support */if (! @ Include_once 'config. inc. php') {file_exists ('./install. ph. under what circumstances can a class be directly referenced without require or include ???

PHP code

  /** Load configuration support */if (! @ Include_once 'config. inc. php') {file_exists ('./install. php ')? Header ('Location: install. php '): print ('missing Config file'); exit;}/** initialize component */Typecho_Widget: widget ('widget _ init '); /** register an initialization plug-in */Typecho_Plugin: factory ('index. php ')-> begin ();/** Start route distribution */Typecho_Router: dispatch ();/** register an end plug-in */Typecho_Plugin :: factory ('index. php ')-> end ();

This is the content of index. php of typecho, where no require or include is seen. how can I directly use the class ???

------ Solution --------------------
How do you know that it is not referenced in config. inc. php?