Making Variables work in Multiple functions

[bosox99]

How can I make Variables work in multiple functions?

Example:

#include <iostream>

using namespace std;

class PlayerMove{
      public:
             void displayBoard(){
           string sp1, sp2, sp3, sp4, sp5, sp6, sp7, sp8, sp9;
          cout << "[" << sp1 << "][" << sp2 << "][" << sp3 << "]" << endl
               << "[" << sp4 << "][" << sp5 << "][" << sp6 << "]" << endl
               << "[" << sp7 << "][" << sp8 << "][" << sp9 << "]" << endl;    
                  }
      
      
      };

int main(){
    
    PlayerMove playerObject;
    playerObject.displayBoard();
    
    
    
    
int exit;
cin >> exit;  
return 0;
   
}

I want the variables sp1 - sp9 to work in all functions. How can I get this to work?