It would be nice to can use as callback class method. It is quite easy to implement.

class RollingCurl { ... function __construct($callback = null, $instance = null) { $this->instance = $instance; $this->callback = $callback; } }

and then call it like this:

if($instance){ $this->instance->$callback; } else if(is_callable($callback)){ call_user_func($callback,...); }

thank you.

Sorry for bothering you. It alredy do the call_user_func(). I should read manual before posting.