self:: referring to derived class in static methods of a parent class
I liked the idea presented in this answer allowing having something like multiple constructors in PHP. The code I have is similar to:
class A {
protected function __construct(){
// made protected to disallow calling with $aa = new A()
// in fact, does nothing
};
static public function create(){
$instance = new self();
//... some important code
return $instance;
}
static public function createFromYetAnotherClass(YetAnotherClass $xx){
// ...
}
class B extends A {};
$aa = A::create();
$bb = B::create();
Now I want to create a derived class B , which would use the same "pseudo-constructor", because it is the same code. However, in this case when I do not code the create() method, the self constant is the class A , so both variables $aa and $bb are of class A , while I wish $bb be class B .
If I use $this special variable, this of course would be class B , even in A scope, if I call any parent method from B .
I know I can copy the entire create() method (maybe Traits do help?), but I also have to copy all "constructors" (all create* methods) and this is stupid.
How can I help $bb to become B , even if the method is called in A context?
You want to use static , which represents the class in which the method is called. ( self represents the class in which the method is defined.)
static public function create(){
$instance = new static();
//... some important code
return $instance;
}
Refer to the documentation on Late Static Bindings.
You'll need PHP 5.3+ to use this.
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