`static` keyword inside function?

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I was looking at the source for Drupal 7, and I found some things I hadn't seen before. I did some initial looking in the php manual, but it didn't explain these examples.

What does the keyword static do to a variable inside a function?

function module_load_all($bootstrap = FALSE) {
    static $has_run = FALSE

Answers

It makes the function remember the value of the given variable ($has_run in your example) between multiple calls.

You could use this for different purposes, for example:

function doStuff() {
  static $cache = null;

  if ($cache === null) {
     $cache = '%heavy database stuff or something%';
  }

  // code using $cache
}

In this example, the if would only be executed once. Even if multiple calls to doStuff would occur.

Saturday, November 26, 2022

suyashnyn1-8ac14df6fb98

If your class is not meant to define some super-type, it should not be declared as abstract, I'd say.

In your case, I would rather go with a class :

That defines __construct and __clone as private methods
- so the class cannot be instanciated from outside
And, this way, your class could create an instance of itself
- See the Singleton design pattern, about that, btw

Now, why use a Singleton, and not only static methods ? I suppose that, at least a couple of reasons can be valid :

Using a singleton means using an instance of the class ; makes it easier to transform a non-singleton class to a singleton one : only have to make __construct and __clone private, and add some getInstance method.
Using a singleton also means you have access to everything you can use with a normal instance : $this, properties, ...
Oh, a third one (not sure about that, but might have its importance) : with PHP < 5.3, you have less possibilities with static methods/data :
- __callStatic has only been introduced in PHP 5.3
- There is no __getStatic, __setStatic, ...
- Same for a couple of other Magic methods !
Late Static Binding has only been added with PHP 5.3 ; and not having it often makes it harder, when working with static methods/classes ; especially when using inheritance.

This being said, yes, some code like this :

abstract class MyClass {
    protected static $data;
    public static function setA($a) {
        self::$data['a'] = $a;
    }
    public static function getA() {
        return self::$data['a'];
    }
}

MyClass::setA(20);
var_dump(MyClass::getA());

Will work... But it doesn't feel quite natural... and this is a very simple example (see what I said earlier with Late Static Binding, and magic methods).

Sunday, September 4, 2022

nava_carmon

Yes 7.1.1/6

A name declared in a namespace scope without a storage-class-specifier has external linkage unless it has internal linkage because of a previous declaration and provided it is not declared const.

`static` keyword inside function?

Answers

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