Question

I can’t quite understand why the output of this code is ‘1’.
My guess is that php is not behaving like most other OO languages that I’m used to, in that the arrays that php uses must not be objects. Changing the array that is returned by the class does not change the array within the class. How would I get the class to return an array which I can edit (and has the same address as the one within the class)?

<?php
    class Test
    {
        public $arr;
        public function __construct()
        {
            $this->arr = array();
        }

        public function addToArr($i)
        {
            $this->arr[] = $i;
        }

        public function getArr()
        {
            return $this->arr;
        }
    }

    $t = new Test();
    $data = 5;
    $t->addToArr($data);

    $tobj_arr = $t->getArr();
    unset($tobj_arr[0]);

    $tobj_arr_fresh = $t->getArr();
    echo count($tobj_arr_fresh);
?>

EDIT: I expected the output to be 0

Answer 1

You have to return the array by reference. That way, php returns a reference to the array, in stead of a copy.

<?php
    class Test
    {
        public $arr;
        public function __construct()
        {
            $this->arr = array();
        }

        public function addToArr($i)
        {
            $this->arr[] = $i;
        }

        public function & getArr() //Returning by reference here
        {
            return $this->arr;
        }
    }

    $t = new Test();
    $data = 5;
    $t->addToArr($data);

    $tobj_arr = &$t->getArr(); //Reference binding here
    unset($tobj_arr[0]);

    $tobj_arr_fresh = $t->getArr();
    echo count($tobj_arr_fresh);
?>

This returns 0.

From the returning references subpage:

Unlike parameter passing, here you have to use & in both places – to
indicate that you want to return by reference, not a copy, and to
indicate that reference binding, rather than usual assignment, should
be done

Note that although this gets the job done, question is if it is a good practice. By changing class members outside of the class itself, it can become very difficult to track the application.