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PHP class: Global variable as property in class

Posted by: admin April 23, 2020 Leave a comment

Questions:

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;

How to&Answers:

You probably don’t really want to be doing this, as it’s going to be a nightmare to debug, but it seems to be possible. The key is the part where you assign by reference in the constructor.

$GLOBALS = array(
    'MyNumber' => 1
);

class Foo {
    protected $glob;

    public function __construct() {
        global $GLOBALS;
        $this->glob =& $GLOBALS;
    }

    public function getGlob() {
        return $this->glob['MyNumber'];
    }
}

$f = new Foo;

echo $f->getGlob() . "\n";
$GLOBALS['MyNumber'] = 2;
echo $f->getGlob() . "\n";

The output will be

1
2

which indicates that it’s being assigned by reference, not value.

As I said, it will be a nightmare to debug, so you really shouldn’t do this. Have a read through the wikipedia article on encapsulation; basically, your object should ideally manage its own data and the methods in which that data is modified; even public properties are generally, IMHO, a bad idea.

Answer:

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');

Answer:

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.)

Answer:

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;

Answer:

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);

Answer:

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

private $classNumber = 8;

Answer:

class myClass
{
protected $foo;

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

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

}