Sending variables between 2 functions

[eluser]luukskywalker[/eluser]
i have a small question

i have 2 functions -> Function_A() and Function B()
and i want to send a variable from function a to function b.
I want something like this(this is just an example):

Code:

Function_a(){
  
  $foo = "1";
  $this->_function_b($foo);
}

Function_b(){
   if($foo){
      
     echo $foo+1;

   }else{

     $foo = "10";
     echo $foo;
   }
}

is this possible?