it is not stipulated that the cast-in-place gatepost must be used. This can be done according to the technical documents issued by the project department. Generally speaking, when the distance between the door and the window is less than 2, the cast-in-place gatepost is used, because it is not good to build bricks when it is less than 2mm, so the cast-in-place doorframe is made.
it is recommended to use the cast-in-place door frame, which is used for all doors smaller than 2mm here.