Call function from another function

[eluser]luukskywalker[/eluser]
is it also possible to send variables from function a to function b?

Because 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;
}