Mirror Effect

ORIGINAL PHOTO

RENAME THE BACKGROUND LAYER

ADD MORE CANVAS SPACE

ADD A VERTICAL GUIDEDOWN THE MIDDLE

SELECT THE MOVE TOOL

MOVE THE PHOTO TO ONE SIDE

SELECT THE IMAGE

SELECT THE TRANSFORM SELECTION COMMAND & DRAG THE LEFT OR RIGHT HANDLE TO THE GUIDE

COPY THE SELECTION TO A LAYER BY SELECT LAYER VIA COPY

SELECT THE FREE TRANSFORM COMMAND 

SELECT FLIP HORIZONTAL

CLICK CLEAR GUIDE

TRIM THE IMAGE

DONE