PHP class: Global variable as property in class

Question

I have a global variable outside my class = $MyNumber;

How do I declare this as a property in myClass?
For every method in my class, this is what

Answer 1

class myClass { protected $foo;

public function __construct(&$var)
{
    $this->foo = &$var;
}

public function foo()
{
    return ++$this->foo;
}

}