php - Back slash to get name space -

so, in router.php file create object of runapp class using namespace. work fine.

namespace router;  // app/routes.php  $runapp= new \core\runapp(); 

in case slash(new \core\runapp()) means need namespace router , try find runapp class in core namespace.

but also, can use link in way:

namespace router;  use core\runapp;  // app/routes.php  $runapp= new runapp(); 

but, why in last case not need set \ befor namespace(use core\runapp)??

note namespaced names (fully qualified namespace names containing namespace separator, such foo\bar opposed global names not, such foobar), leading backslash unnecessary , not recommended, import names must qualified, , not processed relative current namespace.

from php - using namespaces: aliasing/importing

when use use keyword, namespaces not relative, have qualified.
whereas, in other cases, it's relative current namespace.