How do you refuse to create an instance copy in PHP?

Question

In the past, at one interview, I had a test question: "How do you refuse to create a copy of an instance of a class (object)?".

My answer was to use the Singleton patter in the first place, when it denies instantiating at all.

But when I recently thought about it, I think it was not the best answer. Now I think that using a class privatefor a class method __clone()would be a better solution. Thus, it allows you to at least create a new instance.

But I think there is another way to do this? If Singleton is not used or no closed area is set, is there any best practice how to deny instantiating an instance?

Answer 1

There is one more option. When you close your __clone () private account, the following will be called when cloning:

PHP7.x FATAL ERROR Uncaught Error: calling private A :: __ clone () from context

PHP5.x FATAL ERROR Call private A :: __ clone () from context

So, if you want your code to behave exactly the same among different versions of PHP, you can do the following:

<?php

class A {
    public function __clone() {
        throw new Exception('Not allowed to be cloned');
    }
}

$a = new A;
try {
    $b = clone $a;
} catch (Exception $e) {
    echo $e->getMessage(); //Not allowed to be cloned
}

Or more "fancy":

trait NotClonable {
    public function __clone() {
            throw new Exception('Not allowed to be cloned');
    }
}
class A {
    use NotClonable;
}