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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.

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  • 2
    Do you mean stackoverflow.com/questions/24852125/what-is-singleton-in-php/… Commented Aug 29, 2021 at 12:40
  • 1
    No. Assigning to $this doesn't change the instance itself. Implement a singleton class with a method that returns self::$instance. Commented Aug 29, 2021 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. Commented Aug 29, 2021 at 12:42
  • @NigelRen Well, like a singleton class.. But I want to do it using "new Class" and not by Class::getInstance Commented Aug 29, 2021 at 12:44
  • If you have static variables, they will be shared between all classes, is there any reason why you need this? Commented Aug 29, 2021 at 13:20

1 Answer 1

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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.

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