[Description] If this check box is selected, PhpStorm inserts tabs for indentation and reformatting, but fine alignment to a necessary column is done only via spaces without replacing them with tabs. This is done in order to preserve visual representation of the source code, when the Tab Size is changed. If this check box is cleared, only tabs are used. This means that a group of spaces that fits the specified tab size is automatically replaced with a tab, which may result in breaking fine alignment. The Smart Tabs check box is available if the Use Tab Character check box is selected. [Item] 
Smart tabs
U s e t a b c h a r a c t e r
S m a r t t a b s
T a b s i z e
I n d e n t
C o n t i n u a t i o n i n d e n t
K e e p i n d e n t s o n e m p t y l i n e s