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Question

object var $c->$var1 has been changed in class a;

var $new_var has not be changed in function d; i was a litte puzzled. my english is poor,can you understand me?

<?php
    class a{
        public function test () {
            $b = new b;
            $c = new c;
            $b->test($c);
            var_dump($c);
        } 
    }

    class b{
        public function test($c) {
            $c->var1 = 2;
            return $c;
        }
    }

    class c {
        public $var1 = 1;
    }

    $a = new a;
    $a->test();

    function d($new_var) {
        $new_var = 2;
        return $new_var;
    }

    $new_var = 1;
    d($new_var);
    echo $new_var

Answer 1

You problem is that you have this function

function d($new_var) {
        $new_var = 2;
        return $new_var;
}

Where is it true that you maybe pass a different variable as parameter, but then you take that parameter and you decide to set it = 2 and then return it. If you want to return what you passed you should change it in

function d($new_var) {
        return $new_var;
}

Or if you want something similar to test function of class b try tgus

function d($new_var) {
    $d->new_var = $new_var;
    return $d;
}

So you can access to your $new_var in the returned objecd $d