"Please stand up" is the Engpsh translation of "请起立" in Chinese. The phrase is commonly used in formal settings, such as in classrooms or meetings, to request that all those present stand up.
An example of the phrase in use is:
Engpsh: "Please stand up for the national anthem."
Chinese: "请起立默哀国歌。"
Another example:
Engpsh: "Please stand up for roll call."
Chinese: "请起立点名。"
The phrase comes from traditional chinese culture, where people will stand up when they are being addressed by a superior or authority.