bc6443a9_lp____Extract_Interface_Dialog__Item
[Description] In this drop-down list, specify the folder to store the dedicated file created for the new interface. By default, the field is read-only and shows the folder that corresponds to the namespace to which the interface will belong according to the PSR0 standard. To have the class with the interface stored in another folder, click F2 and specify the folder of your choice. [Item] 
Target destination directory
PhpStorm 8.0.2 Help :: Extract Interface Dialog