Confused about permissions of a member in php

The permissions of a member in php are confusing: & lt ;? Phpclass & nbsp; Far {& nbsp; protected & nbsp; $ arr; & nbsp; protected & nbsp; function & nbsp; init () & nbsp; {& nbsp; the permission of a member in php is confusing.
Problem: The following code is available:
Class Far
{
Protected $ arr;

Protected function init (){
Foreach ($ this-> arr as $ k => $ val ){
$ This-> $ k = $ val;
}
}

Public function _ construct (){
$ This-> init ();
}

Public function _ set ($ name, $ val ){
$ This-> $ name = $ val;
}
}

Class Son extends Far
{
Protected $;

Public function _ construct (){
$ This-> arr = array (
'A' => '1 ',
);

Parent: :__ construct ();
}
}

$ Obj = new Son ();
Print_r ($ obj );
Q: Why is a null instead of 1 in the output result of $ obj.
Son Object
(
[A: protected] => 1
[Arr: protected] => Array
(
[A] => 1
)

)

Question 2: If you change the private $ a of the subclass to protected $ a or public $ a in the above code, the output is:
Son Object
(
[A: protected] => 1
[Arr: protected] => Array
(
[A] => 1
)

[Bb] => 1
)

Why?
------ Solution --------------------
Your _ set method is defined in Far, so he cannot access Son's private attributes.
You can write it in this way.

class Far {
    protected $arr;
    protected function init() {
        foreach ($this->arr as $k => $val) {
            $this->$k = $val;
        }
    }

    public function __construct() {
        $this->init();
    }

    public function __set($name, $val) {
        $this->$name = $val;
    }
}

class Son extends Far {
    private $a;
    public function __construct() {
        $this->arr = array(
            'a' => '1',
        );
        parent::__construct();
    }
    public function __set($name, $val) {
        $this->$name = $val;
    }
}

$obj = new Son();
print_r($obj);

Son Object
(
[A: Son: private] => 1
[Arr: protected] => Array
(
[A] => 1
)

)