PHP | is it possible to set new class instance to be the same as exists instance?

Question

I'm currently looking for a way to set a new instance to be the same as an exists instance if already exists.

Is there any easy way as doing something like:

Class Check {
    public static $instance = null;
    public $name = "";

    function __construct($name) {
        if (self::$instance !== null) {
            $this = self::$instance;
        } else {
            $this->name = $name;
            self::$instance = $this;
        }
    }
}

$a = new Check("A");
$b = new Check("B");
echo $a->name." = ".$b->name;

to achieve it?

what it returns:

A =

What I want it to return:

A = A

Is it possible to accomplish that? I want that all variables of the older instance to maintain the same.

Thanks in advance.

Do you mean https://stackoverflow.com/questions/24852125/what-is-singleton-in-php/24852235 — Nigel Ren, Aug 29 '21 at 12:40
No. Assigning to `$this` doesn't change the instance itself. Implement a singleton class with a method that returns `self::$instance`. — Barmar, Aug 29 '21 at 12:40
@Barmar Yea I've saw it and edited my question. but you can understand my needs from the question. I know I can't do it like that.. but is there any easy option like what I've showed. — bado yasi, Aug 29 '21 at 12:42
@NigelRen Well, like a singleton class.. But I want to do it using "new Class" and not by Class::getInstance — bado yasi, Aug 29 '21 at 12:44
If you have static variables, they will be shared between all classes, is there any reason why you need this? — Nigel Ren, Aug 29 '21 at 13:20
The keyword `new` is intended to explicitly create a new instance. It is basically a hint on the calling side that a dedicated unique instance is being requested. Changing the semantics of `new` would be very confusing. So the short answer is “no, this is not possible”. As everyone else says, that’s why the singleton pattern exists. — Chris Haas, Aug 29 '21 at 14:04

bado yasi · Answer 1 · 2021-08-30T07:58:28.550

This is the only two ways I found to achieve it

#1 Using get_object_vars

You can use get_object_vars that returns all public variables that a specific object contains, then you can iterate them using foreach

example:

if (self::$instance !== null) {
    foreach (get_object_vars(self::$instance) as $prop=>$value) {
        $this->{$prop} = $value;
    }
}

#2 Is using PHP reflection, I find it less useful in my case because it doesn't reflect properties that was generated on the go

Note: Reflection will reflect also properties such as private|static and so. you can filter them inside the getProperties function or iterate through all properties and use boolean methods filter between them.

example:

if (self::$instance !== null) {
    $reflection = new ReflectionClass(self::$instance);
    $props = $reflection->getProperties();
    foreach ($props as $prop) {
        $this->{$prop->name} = $prop->getValue(self::$instance);
    }
}

so if you do self::$instance->newVar = 1; it won't be reflected. but in the #1 Option it will be.

Hope it will help someone out there.

PHP | is it possible to set new class instance to be the same as exists instance?

1 Answers1