[SOLVED] How do I call a static method from an unknown class?

[Salim]

Hi,

I have a strange problem, but I really need to figure out how this works.

 

abstract class A
{
  function A() { echo "constr. A"; }
  static abstract function foo();
}

class B extends A
{
  function B() { echo "constr. B"; }
  static function foo() { echo "B::foo"; }
}

class C extends A
{
  function C() { echo "constr. C"; }
  static function foo() { echo "C::foo"; }
}

function getClName()
{
  return C;
}

$clname = getClName();
// $obj = new $clname(); // this would work
$clname::foo(); // this does not work! how can I make this work?

 

I think you can see my problem. I want to call a static method of a class I don't know. It works perfectly when constructing an object and calling its non-static methods. But how can I call its static methods without creating an object from it?

 

greetings, Salim

[Zane]

try returning a new C instance

function getClName()
{
  return new C;
}

[Salim]

No it doesn't work. Anyway, what if the constructor expects parameters? In that case it wouldn't work when creating an object before.

[duclet]

I don't think PHP currently has support for that.

[deadimp]

You can use the new object construction as zanus suggested and just use the -> operator, as long as you don't put the static keyword in front of your method declaration. PHP is lenient on calling functions statically. You can call any function using the static member operator :: and it'll work up until a $this reference. That gets a little awkward though, and you've already used the static keyword.

 

Another way would be to look at call_user_func() and see how you can format callback:

mixed call_user_func  ( callback $function  [, mixed $parameter  [, mixed $...  ]] )

function - The function to be called. Class methods may also be invoked statically using this function by passing array($classname, $methodname) to this parameter.

So in this context:

$class=getClName(); //Returns a string "C"
call_user_func(array($class,"foo")); //Calls C::foo()

You can add whatever parameters you want. Also look at call_user_func_array() if you want some more flexiblity.

 

EDIT: Fixed the error Anthop pointed out. Otherwise it would have executed C("foo") instead of C::foo().

[Anthop]

deadimp's suggestion seems very promising.

 

Also, I'm not sure, but I think to correctly call a static function, C::foo() in this case, you would have to actually use:

call_user_func(array($class, "foo"));

[Salim]

Thanks a lot. This works fine. Although $clname::foo(); would have been much nicer (what a pity it doesn't work), call_user_func helps.