friend function in php?

Question

Does php support friend function like as c++ supports?

Looks like it doesn't: http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=friend+function+php and even Wikipedia seems doesn't mention it: http://en.wikipedia.org/wiki/Friend_function — fabrik, Sep 14 '10 at 09:03
possible duplicate of [PHP equivalent of friend or internal](http://stackoverflow.com/questions/317835/php-equivalent-of-friend-or-internal) — , Jun 11 '12 at 21:19

score 7 · Accepted Answer · answered Sep 14 '10 at 09:10

You are most likely referring to class/variable scope. In php, you have:

public
private
protected

But not friend visibility. The protected though is used when an object's members are to be made visible only to other extending/inheriting objects.

More Info:

http://php.net/manual/en/language.oop5.visibility.php

score 3 · Answer 2 · answered Sep 14 '10 at 09:06

3

No. You have to declare it public.

answered Sep 14 '10 at 09:06

troelskn

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score 2 · Answer 3 · answered Mar 08 '15 at 07:39

PHP doesn't support any friend-like declarations. It's possible to simulate this using the PHP5 __get and __set methods and inspecting a backtrace for only the allowed friend classes, although the code to do it is kind of clumsy.

There's some sample code and discussion on the topic on PHP's site:

class HasFriends { private $__friends = array('MyFriend', 'OtherFriend');

public function __get($key)
{
    $trace = debug_backtrace();
    if(isset($trace[1]['class']) && in_array($trace[1]['class'], $this->__friends)) {
        return $this->$key;
    }

    // normal __get() code here

    trigger_error('Cannot access private property ' . __CLASS__ . '::$' . $key, E_USER_ERROR);
}

public function __set($key, $value)
{
    $trace = debug_backtrace();
    if(isset($trace[1]['class']) && in_array($trace[1]['class'], $this->__friends)) {
        return $this->$key = $value;
    }

    // normal __set() code here

    trigger_error('Cannot access private property ' . __CLASS__ . '::$' . $key, E_USER_ERROR);
}

}

friend function in php?

3 Answers3

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