PHP self:: vs static::

[Ray]

In this code snippet, I get output that says "keykey"

What is the difference between the meanings of static:: and self:: in
this or any other context. Any man page reference would be gratefully
received!

<?php
error_reporting(E_ALL);

Class Thing
{
const PRIMARY_KEY = 'key';

public function keys()
{
$x = self::PRIMARY_KEY;
$y = static::PRIMARY_KEY;
return $x . $y;
}
}

$thing = new Thing;
var_dump($thing->keys());

Thanks and regards, Ray

[Oscar]

Inheritance is where this really shows up.

- static:: refers to the calling class, ie " references the class that was initially called at runtime. "
- self:: refers to the class that actually defined the method

About static:

http://us2.php.net/manual/en/language.oop5.static.php

In particular, see the examples here:

http://us2.php.net/manual/en/language.oop5.late-static-bindings.php

Since :: is the scope resolution operator, you can remember the distinction as "'self' limits the scope to the defining class"

[John Bloch]

static:: uses late static binding whereas self does not. If you were to extend Thing and redefine PRIMARY_KEY (say, to 'foobar'), running keys() on an instance of that subclass would return 'keyfoobar'.

Put another way, self:: always refers only to the class it is written in, while static:: refers to the class context in which it is run.

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[Tim Jarrett]

You need to check out this page. For PHP 5.3+

If I understand correctly static:: will refer to the last called class whereas self:: always refers to self. Check out this example (based on yours):

<?php
error_reporting(E_ALL);

Class Thing
{
    const PRIMARY_KEY = 'key';

    public function keys()
    {
        $x = self::PRIMARY_KEY;
        $y = static::PRIMARY_KEY;
        return $x . $y;
    }
}

class Thing2 extends Thing
{
    const PRIMARY_KEY = 'key2';

   
}

$thing = new Thing;
var_dump($thing->keys());

$thing2 = new Thing2();
var_dump($thing2->keys());

And that outputs:
string(6) "keykey"
string(7) "keykey2"

Make sense?