PHP static function as parameter with dependency injection

Question

I'd like to call a static function of class A, in class B by passing it via Start.php as a parameter, but without including the ClassA.php into ClassB.php.

The reason I want to do this is because I have some client-specific logic, that i want to separate and call centrally and only when I really need it (index.php) without including it in the other files.

Let's say I've 3 files.

Start.php, ClassA.php, ClassB.php

ClassA.php

class A {

  public static function foo($param) {
    // do some special logic
    // and return either true or false
  }

}

ClassB.php

class B {

    function bar($var, $func) {
      foreach($var as $v) {
        if($func($var)) {
          echo 'OK';
        }
      }
    }

}

Start.php

require_once('ClassA.php');
require_once('ClassB.php');

class Start() {

  function init() {
    $b = new B();
    $test = array(1,2,3,4,5);
    $b->bar($test, ['A', 'foo']);
  }
}

Start::init();

So, Start depends on ClassA and ClassB, that's OK.

But I don't want ClassB to depend on ClassA.

When I do it like this, I get error, saying that Class A cannot be found.

Is that possible? Is that even considered as good practice?

Answer 1

I think you're going about this the wrong way. In fact, the syntax you're using here has been changed in PHP7. Let's clean this up

class B {
    function bar($var, $func) {
      $method = $func[0] . '::' . $func[1];
      foreach($var as $v) {
        if(call_user_func($method, $v)) {
          echo 'OK';
        }
      }
    }
}

So what we're doing here is we're telling PHP to use the static function in your array and then directly calling it using the precise call_user_func function (this is considered a best practice). Please note that I assumed that your call will always be static but it will work with any class you pass in that way.

You can see this in action here https://3v4l.org/WpeiD

Answer 2

我必须为函数调用提供完整的名称空间，因此：

$b->bar($test, ['my\\namespace\\A', 'foo']);