Cake3のview#extend()のヒエラルキー（読み込み順序）

attachment plugin の中にいる前提です。

相対

$this->extend('Cirici/AdminLTE/Common/index');

読み込み順

$APP/vendor/funayaki/adminlte/src/Template/Plugin/Attachments/Admin/Attachments/Cirici/AdminLTE/Common/index.ctp
$APP/vendor/funayaki/adminlte/src/Template/Admin/Attachments/Cirici/AdminLTE/Common/index.ctp
$APP/src/Template/Plugin/Attachments/Admin/Attachments/Cirici/AdminLTE/Common/index.ctp
$APP/vendor/funayaki/attachments/src/Template/Admin/Attachments/Cirici/AdminLTE/Common/index.ctp
$APP/src/Template/Admin/Attachments/Cirici/AdminLTE/Common/index.ctp

相対、ピリオド（プラグインでよく見るやつ）

$this->extend('Cirici/AdminLTE./Common/index');

読み込み順

$APP/vendor/funayaki/adminlte/src/Template/Plugin/Attachments/Common/index.ctp
$APP/vendor/funayaki/adminlte/src/Template/Common/index.ctp
$APP/src/Template/Plugin/Attachments/Common/index.ctp
$APP/vendor/funayaki/attachments/src/Template/Common/index.ctp
$APP/src/Template/Common/index.ctp

絶対

$this->extend('/Cirici/AdminLTE/Common/index');

読み込み順

$APP/vendor/funayaki/adminlte/src/Template/Plugin/Attachments/Cirici/AdminLTE/Common/index.ctp
$APP/vendor/funayaki/adminlte/src/Template/Cirici/AdminLTE/Common/index.ctp
$APP/src/Template/Plugin/Attachments/Cirici/AdminLTE/Common/index.ctp
$APP/vendor/funayaki/attachments/src/Template/Cirici/AdminLTE/Common/index.ctp
$APP/src/Template/Cirici/AdminLTE/Common/index.ctp