Limitations of self::

Static references to the current class like self:: or __CLASS__ are resolved using the class in which the function belongs, as in where it was defined:

A

    

Late Static Bindings' usage

Late static bindings tries to solve that limitation by introducing a keyword that references the class that was initially called at runtime. Basically, a keyword that would allow you to reference B from test() in the previous example. It was decided not to introduce a new keyword but rather use static that was already reserved.

B

    

Note: static:: does not work like $this for static methods! $this-> follows the rules of inheritance while static:: doesn't. This difference is detailed later on this manual page.

TestChild
TestParent

    

Note: Late static bindings' resolution will stop at a fully resolved static call with no fallback. On the other hand, static calls using keywords like parent:: or self:: will forward the calling information.

Example #4 Forwarding and non-forwarding calls

<?php
class A {
    public static function foo() {
        static::who();
    }
        
    public static function who() {
        echo __CLASS__."\n";
    }
}

class B extends A {
    public static function test() {
        A::foo();
        parent::foo();
        self::foo();
    }

    public static function who() {
        echo __CLASS__."\n";
    }
}
class C extends B {
    public static function who() {
        echo __CLASS__."\n";
    }
}

C::test();
?>

The above example will output:

A
C
C

     

Edge cases

There are lots of different ways to trigger a method call in PHP, like callbacks or magic methods. As late static bindings base their resolution on runtime information, it might give unexpected results in so-called edge cases.

B