Example i write:
if ABC read the post, it become:
I want use variable in the post to show weather, chatbox,...
But i don't know how to make a variable in the post.
Please help me

That can be done if you put your PHP codes inside bb_plugins.php or bb_plugins_user.php. I don't know exactly what the differences in these files are.

There is no easy way to do this in miniBB. Else it would be too insecure. miniBB uses such default PHP tags to parse templates, not user's input.

For user's input, you will need to create a standalone BB code/tag. Each code could be transformed into something and back. Refer to how Youtube or Vimeo codes are implemented, something similar will work for your tasks, too.

It seem like function: makeUp or praseTpl. when a user submit a query, it have some change. Of course, i must have an array which variables are applied. if not, sb can show my password :). But I don't know how to do it exactly.

I'm not sure what do you mean.
Do you mean, there is some possibility to pass such templates in miniBB, using message form?
What kind of query do you mean?
What is "sb"?

sb=somebody.
Yes, I want use for post message
Example:
User can write [birthday=5] to show birthday of user_id 5 in post message, for example.
I also want use this feature for more addon in the future, example: [weather=city_number], [timetable=student_id],...
And i want use it in post message, not in seperate pages.

I miss the logics of it. For displaying a birthday, you may install the proper solution.

You obviously include some of your own code, and that could cause the errors or something suspicious you see appearing. I don't know what your code is about. What I know, in miniBB, there should be no such "hack" possible.

In other words, what you try to implement, requires different approach. It all should be possible done via JavaScript. BB code is transformed into JS call, and JS call is a standalone script, which parses and gets the data from DB, based on the passed input.

oh. You can found it in Poll Addon

Poll add-on? You can found it?..
What does it mean :)

Thank omg.
Now the task has done!

If I understand correctly, the approach of replacing BB code to JavaScript is also used in Polls add-on, that's correct.

But it must be convert from [birthday=1] to real birthday at php sever.
Once again, thank Omg and Paul

It's up to you how you build this algorithm. There is nothing difficult, if you take care to analyze the mentioned add-ons.