Why does PHP support calling static functions as non-static member methods?

Question

Code beforehand fully valid code from 5.0.0 (without E_STRICT or E_DEPRECATED)

class A{
    static public function b() {
    }

    public function c(){
        $this->b();
    }
}

$d = new A();
$d->c();
$d->b();

It's looks like inconsistent behaviour because you cannot use static properties from instance.

The PHP way is to steal and borrow from other languages whenever possible ...

But I cannot find any programming language that supports similar behavior.

Why does PHP support it? What is the point of calling static methods as non-static?

Some explanation from support: Expected behavior

I would assume because it was misscorrectly tagged as Duplicate, when it wasn't @PaulCrovella. — Blue
– Blue, Commented Oct 23, 2018 at 11:44
I agree 100% @PaulCrovella. I'm only speculating as to why the OP did what he did. — Blue
– Blue, Commented Oct 23, 2018 at 11:47
@PaulCrovella, it was closed as duplicated. It's hard to restore question from there. Deleted question should not appear in reopen queue. — sectus
– sectus, Commented Oct 23, 2018 at 12:34
@sectus The easiest way is to ping @Phil, and explain to him why it's not a reason. Had you explained in a comment/edit that this is a request for reasoning, and that dupe target has absolutely no developer reasoning, I'm sure others would agree with you (I personally would have voted to reopen). — Blue
– Blue, Commented Oct 23, 2018 at 12:40

Blue · Accepted Answer · 2018-10-23 12:47:29Z

2

Actually, C++ and Java support this. It seems the PHP developers, after discussion, decided on implementation to match them.

After a bit of digging, I found this thread from February 2004, which is essentially their discussion about the implementation choices. Important tidbits from the discussion:

From Cristiano Duarte:

C++ allows $a->bar() when bar() is a static method (yes, it is called in a static context there too).

IMO, there should be no error, warning or notice here.

I Agree. PHP is fine the way it is.

From Art:

Regardless of the final implementation, I think access to static methods and static class variables should be consistent. Currently, you cannot access a class variable via an object instance.

And for what it's worth, I see no reason why static methods cannot be called from objects. Follow Java/C++ in this case.

Ultimately, a final decision From Wez:

Please drop this thread; we're not changing the behaviour of static.

edited Oct 23, 2018 at 12:47

answered Oct 23, 2018 at 12:04

Blue

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3 Comments

sectus Over a year ago

It is a little bit tricky to call static method of parent class of instance in Java.

Blue Over a year ago

@sectus I agree, and the full thread goes into a little bit more detail on that. (I recommend giving it a full read, if you're curious).

sectus Over a year ago

Sure, I am curious.

Kaddath · Accepted Answer · 2018-10-23 12:03:34Z

1

It looks to me that it is just a syntax consideration here. Nothing here is inconsistent with the logic of static methods, it's still impossible to use $this in your static function, and therefore the function will not have access to instance properties or methods. It feels more like a shortcut than an inconsistency to me.

I have no use case of that, but I guess someone may find it useful with objects created with dynamic class names: you can still use the function even if you don't know it's class name.

answered Oct 23, 2018 at 12:03

Kaddath

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2 Comments

sectus Over a year ago

Why static properties cannot be used in the same way?

Kaddath Over a year ago

this can seem inconsistent, yes, but it's actually possible to get a static property from an instance with the syntax $d::$b, though you cannot use the arrow here, which is a bit inconsistent syntax i admit

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