Can I make this code shorter?
Is it possible to do?
If it is, how?
By using functions. You can move common code to a named function.
This is C code not C++.
Sure it compiles with a C++ compiler (so does a lot of C). C++ is a style of programming, you are not using the C++ style you are using the C style of programming.
There is no better way to say this, but your code is shockingly bad. I will just provide a short summary of the things that can be improved:
#include headers like everyone else does, don't forward declare standard library functions.
Since you tagged the post C++, use C++'s iostream functionality; it gives you type safety.
Split your program into several ...
This is not a full review, but try using functions actually used in modern C++. There is no point in using printf() and scanf(), as they are just in the language for C-portability. std::cout and std::cin would be the C++ equivalents (you have to #include <iostream>).
I'd recommend looking at the accepted PSRs - e.g. PSR-1, PSR-12. Updating the code to comply with them will help make the code readable and consistent with idiomatic PHP code.
Maybe this is just a copy-paste issue, but even if you don't strictly follow PSR-12 please indent nested lines within blocks.
As of the time of writing, PHP 7 ...