Question

I’m trying to configure an object at runtime passing a callback function like so:

class myObject{
  protected $property;
  protected $anotherProperty;

  public function configure($callback){
    if(is_callable($callback)){
      $callback();
    }
  }
}

$myObject = new myObject(); //
$myObject->configure(function(){
  $this->property = 'value';
  $this->anotherProperty = 'anotherValue';
});

Of course I get the following error:

Fatal error: Using $this when not in object context

My question is if there is a way to achieve this behavior using $this inside a callback function or maybe get a suggestion for a better pattern.

PS: I prefer to use a callback.

Answer 1

Starting with your idea, you could pass $this as a parameter to your callback

But note that your callback (which is not declared inside your class) will not be able to access protected nor private properties/methods — which means you’ll have to set up public methods to access those.

Your class would then look like this :

class myObject {
  protected $property;
  protected $anotherProperty;
  public function configure($callback){
    if(is_callable($callback)){
      // Pass $this as a parameter to the callback
      $callback($this);
    }
  }
  public function setProperty($a) {
    $this->property = $a;
  }
  public function setAnotherProperty($a) {
    $this->anotherProperty = $a;
  }
}

And you’d declared you callback, and use it, like this :

$myObject = new myObject(); //
$myObject->configure(function($obj) {
  // You cannot access protected/private properties or methods
  // => You have to use setters / getters
  $obj->setProperty('value');
  $obj->setAnotherProperty('anotherValue');
});

Calling the following line of code just after :

var_dump($myObject);

Would output this :

object(myObject)[1]
  protected 'property' => string 'value' (length=5)
  protected 'anotherProperty' => string 'anotherValue' (length=12)

Which shows that the callback has been executed, and the properties of your object have indeed been set, as expected.