Call callback stored as member variable

Question

Is it possible with php to directly call a callback stored in an member variable of a class? currently I'm using a workaround, where I'm temporarily storing my callback to a local var.

class CB {
  private $cb;
  public function __construct($cb) {
    $this->cb = $cb;
  }
  public function call() {
    $this->cb(); // does not work
    $cb = $this->cb;
    $cb(); // does work
  }
}

php complains that $this->cb() is not a valid method, i.e. does not exist.

Similar question asked and answered [here](http://stackoverflow.com/questions/1656151/php-callable-object-as-object-member). Cliff notes version: "Mostly because of the loose typing. There's no way of actually infering what you might mean to do, so it defaults to erroring early." — Problematic, Aug 10 '11 at 15:10
Perhaps `{$this->cb}()`? The `{}` should force PHP to see the cb reference as the `$cb` member var, and not as a cb method in the object. — Marc B, Aug 10 '11 at 15:37
@FooBah: allowing users of the class to provide a log function (see the question [PHP Callable Object as Object Member](http://stackoverflow.com/questions/1656151/php-callable-object-as-object-member)) — knittl, Aug 10 '11 at 16:09

score 10 · Answer 1 · answered Apr 24 '17 at 15:25

10

In php7 you can call it like this:

class CB {
  /** @var callable */
  private $cb;
  public function __construct(callable $cb) {
    $this->cb = $cb;
  }
  public function call() {
    ($this->cb)();
  }
}

answered Apr 24 '17 at 15:25

red_led

343
4
7

score 6 · Accepted Answer · answered Aug 10 '11 at 16:43

6

You need to use call_user_func:

class CB {
    private $cb;
    public function __construct($cb) {
        $this->cb = $cb;
    }
    public function call() {
        call_user_func($this->cb, 'hi');
    }
}

$cb = new CB(function($param) { echo $param; });
$cb->call(); // echoes 'hi'

answered Aug 10 '11 at 16:43

Matthew

15,464
2
37
31

A pity I cannot call it directly, but I guess there's no way around using either `call_user_func` or storing the callback in a local var. Seems like the PHP parser is quite limited in some regards. `call_user_func` is as good as it gets, thanks! – knittl Aug 10 '11 at 16:47

Call callback stored as member variable

2 Answers2