[php] PHP class: Global variable as property in class

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 I do:

class myClass() {

    private function foo() {
         $privateNumber = $GLOBALS['MyNumber'];
    }

}

I want this

class myClass() {

    //What goes here?
    var $classNumber = ???//the global $MyNumber;

    private function foo() {
         $privateNumber = $this->classNumber;
    }

}

EDIT: I want to create a variable based on the global $MyNumber but
modified before using it in the methods

something like: var $classNumber = global $MyNumber + 100;

What about using constructor?

class myClass {

   $myNumber = NULL;

   public function __construct() {
      global myNumber;

      $this->myNumber = &myNumber; 
   }

   public function foo() {
      echo $this->myNumber;
   }

}

Or much better this way (passing the global variable as parameter when inicializin the object - read only)

class myClass {

   $myNumber = NULL;

   public function __construct($myNumber) {
      $this->myNumber = $myNumber; 
   }

   public function foo() {
      echo $this->myNumber;
   }

}
$instance = new myClass($myNumber);

Simply use the global keyword.

e.g.:

class myClass() {
    private function foo() {
        global $MyNumber;
        ...

$MyNumber will then become accessible (and indeed modifyable) within that method.

However, the use of globals is often frowned upon (they can give off a bad code smell), so you might want to consider using a singleton class to store anything of this nature. (Then again, without knowing more about what you're trying to achieve this might be a very bad idea - a define could well be more useful.)

class myClass { protected $foo;

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

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

}

Try to avoid globals, instead you can use something like this

class myClass() {
 private $myNumber;

 public function setNumber($number) {
  $this->myNumber = $number;
 }
}

Now you can call

$class = new myClass();
$class->setNumber('1234');

What I've experienced is that you can't assign your global variable to a class variable directly.

class myClass() {

    public $var = $GLOBALS['variable'];

    public function func() {
         var_dump($this->var);
    }
}

With the code right above, you get an error saying "Parse error: syntax error, unexpected '$GLOBALS'"

But if we do something like this,

class myClass() {

    public $var = array();

    public function __construct() {
        $this->var = $GLOBALS['variable'];
    }

    public function func() {
         var_dump($this->var);
    }

}

Our code will work fine.

Where we assign a global variable to a class variable must be inside a function. And I've used constructor function for this.

So, you can access your global variable inside the every function of a class just using $this->var;

If you want to access a property from inside a class you should:

private $classNumber = 8;