Static vs Instantiated Classes/Methods

amnesia623

I'm a little confused on when to use a static method as opposed to a instatiated method.

I unerstnd that static means the the method is available to the entire script ($me = idont::know) but when is this good to use as opposed to instantiated methods?

Thanks!

laserlight

amnesia623 wrote:
I'm a little confused on when to use a static method as opposed to a instatiated method.

I think you mean a static (or class) method versus a non-static (or instance) method.

amnesia623 wrote:
I unerstnd that static means the the method is available to the entire script ($me = idont::know) but when is this good to use as opposed to instantiated methods?

If the method uses non-static data members, then it must be a non-static method. If it uses static data members but not non-static data members, then it probably should be a static method. (If it uses no data members at all, or only uses data members via other methods, then it probably should not be a method of the class.)

Of course, this means that you now have to decide whether a data member should be static or non-static, and that means asking the question of whether it is specific to each instance of the class, or if it should be shared by all the instances of the class.

Also, until namespaces become available (very soon), you could also use a class with only static methods as a poor man's version of a namespace.

amnesia623

I know it's been a few days on this, but thanks.

I did some reading on namespaces and they look great, but i need to get a solid grip on some other things first.

Now, I was told that static methods are good when you want to include these methods within other classes. Is this right?

laserlight

amnesia623 wrote:
I was told that static methods are good when you want to include these methods within other classes.

What do you mean by "include these methods within other classes"?

amnesia623

ok - admittedly this will be rough but here's the jist of what/how I understood it:


class Letters  {

static $letters;

static function  DoLetter() {
$letters = "abc";
return $letters;
  };

}

class Numbers {

   public $numbers;

   public function DoNumbers() {
   $numbers = "123";
   return Letters::DoLetters() . $numbers ;
  };

}

$LettersNumbers = new Numbers->DoNumbers();
echo LettersNumbers;

Is this right? I am still searching for a purpose of static vars/methods, is this one?

Thanks!

NogDog

I think this article gives a pretty good overview of the topic. (It's Java-oriented, but still applicable to PHP.)

I tend to go by the "rule" I read somewhere or other of only declaring class members as static when you find that you actually need to (i.e., not just because you can).

laserlight

amnesia623 wrote:
admittedly this will be rough but here's the jist of what/how I understood it:

You are using the Letters class primarily as a means of simulating a namespace what the article that NogDog links to calls a utility class). The static member variable is not actually used, and indeed it is unnecessary since a local variable will do.

NogDog wrote:
I think this article gives a pretty good overview of the topic. (It's Java-oriented, but still applicable to PHP.)

It looks like a good article. That said, I detect something bogus towards the end:

Utility classes are an excellent place to put methods that you would have otherwise put into a subclass.

I regard the statement as flawed as it suggests that inheritance be used to reuse implementation rather than for Liskov substitutability. On the contrary, if a utility class is an excellent place to put a method, then putting it into a subclass instead is likely to be bad design, if it were even possible.