src/components/Handler.php
public function with_callback( $callback = '', $callback_args = array() ) {

		$this->handle_callback      = $callback;
		$this->handle_callback_args = $callback_args;

		return $this;
	}
public function with_callback( $callback = '', $callback_args = array() ) {

		$this->handle_callback      = $callback;
		$this->handle_callback_args = $callback_args;

		return $this;
	}
Registers the callback function to handle the request.

@param mixed $callback      The callback function (function name, class method, or closure).
@param array $callback_args Arguments to be passed to the callback.

@return Handler