shared variable across multiple class instances that I can change outside the class

the code explains it better:

class Class{
  $var = 0;

  function getvar()
    echo $this->var;
  }

}



$inst1 = new Class();

// I want to change $var here to 5

$inst2 = new Class();

echo $inst2->getvar(); // should be 5

Is it possible