[RESOLVED] A question regarding static methods...

nrg_alpha

Ok.. I have been diverted from classes for a while.. slowly getting back to tackling them.

I'm rather confused specifically with 'static methods'. I can understand making public properties static if you want to access them directly from outside a class without needing to create an object, as without the static key word, these properties rely on instantiated objects (in other words, sans-static, you cannot simply echo out a public property (say $myProperty) from a class (say myClass) as such - echo myClass::$myProperty).

Where I'm not so sure however, is when dealing with static methods... From what I can gather, so long as methods are a) not private nor protected nor final, etc.. and b), there is no pseudo variable $this involved, on the onset it would seem that it doesn't matter if they are declared static or not:

class user {
   public function myFunc(){
        return 'Welcome to myFunc' . "<br />\n";
   }
}
echo user::myFunc();

This works, as it is public, and there is no $this placeholder (which common sense would denote the need to create an object to make use of). But whether I include the keyword static or not next to public in the above method, I will be able to call it statically it appears...

Am I sorely missing something here? I have tried finding examples that require the static keyword on a method.. perhaps I overlooked something?

Cheers

laserlight

nrg_alpha wrote:
This works, as it is public, and there is no $this placeholder (which common sense would denote the need to create an object to make use of). But whether I include the keyword static or not next to public in the above method, I will be able to call it statically it appears...

As the PHP manual entry on the static keyword notes: "Calling non-static methods statically generates an E_STRICT level warning." The reason that I can think of is that if you call a non-static method statically, it may work now, but if the implementation changes such that the non-static method uses a member variable, it will no longer work.

Weedpacket

laserlight has already noted the "optional" nature of the static keyword - basically it's for backwards-compatibility with PHP 4, which didn't have the keyword.

Aside from that, I'm guessing the rationale behind having static methods as such is not an issue?

nrg_alpha

Thanks for the response guys (guy and gal).

@ laserlight: Ah, yes... I was tesing using:

error_reporting(E_ALL);

Now that I added E_STRICT, I see the warning! 😉 My bad, must have missed that...

@ Weedpacket: I wasn't aware that PHP 4 didn't those keywords (didn't tackle classes in PHP 4... from what I hear, that's a good thing).
Perhaps it is all a non issue.. I just find myself scratching my head about it, as from how I see it, the only time you can call a static method (with or without the static keyword) is if it's pretty much public and there is no $this variable involved (which seems to negate the static keyword in the first place [E_STRICT warning not withstanding]).

So perhaps as laserlight mentioned, it is for possible future implementations... so static keyword it is!

Thanks again guys.

NogDog

Using the static keyword will also make your interface clearer: if you declare a method as static then it is immediately apparent to the client coder that it is intended to be available for static use. Also, it forces the method to act in a static mode; e.g. the following code will generate a run-time fatal error:

<?php
class Test
{
   public $bar = 1;

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

$test = new Test();
$test->foo();
?>

Output:

Fatal error: Using $this when not in object context in C:\wamp\www\test\test.php on line 8

So once you declare a method as static, you are forced to code it as such (though unfortunately no parse error is generated; you only discover the error when you actually try to call the method).

nrg_alpha

Yeah, there's no doubt about clairy, as the same principal can be said about declaring a property or method public.. as by default, without any declarations, they are understood as such (granted, static is not assigned be default).

So when I see your example, I know right way that this is problematic, as the psudeo variable $this is involved in conjunction with the static declaration.

By the way, are you sure you do not mean? :

echo $this->bar;

But for sure, assuming the function is set up properly to be staticically called, it definitely makes it clear to whomever coding to see the static keyword.

NogDog

nrg_alpha;10902072 wrote:
...
By the way, are you sure you do not mean? :
echo $this->bar;
...

Yeah, I changed it to self::$bar to make sure I wasn't confused about what was going on, then when I changed it back to $this-> I forgot to remove that "$".