<?php

class A {

    protected $_a = [];
    public function __call($name, $args) {
        if (is_callable($this->$name)) {
            return call_user_func($this->$name, $args);
        } else {
            throw new \RuntimeException("Method {$name} does not exist");
        }
    }

    public function __set($name, $value) {
        $this->$name = is_callable($value) ?
                $value->bindTo($this, $this) :
                $value;
    }
    public function geta() {
        return $this->_a;
    }

}
$a = new A;
$a->foo = function() {
    $this->_a[] = 'asasas';
    $this->_a[] = 'asasas1';
    $this->_a[] = 'asasas2';
};
$a->foo();
var_dump($a->geta());