Property Name from Another Object in OOP in PHP

A property name can even be a property of another object. Let's say we have the following class User:

<?php
	class User
	{
		public $name;
		public $surn;
		
		public function __construct($name, $surn)
		{
			$this->name = $name;
			$this->surn = $surn;
		}
	}
?>

Let's create an object of this class:

<?php
	$user = new User('john', 'smit');
?>

Let's also say we have a class Prop, which will store the name of a property in its value property:

<?php
	class Prop
	{
		public $value;
		
		public function __construct($value)
		{
			$this->value = $value;
		}
	}
?>

Let's create an object of this class:

<?php
	$prop = new Prop('name'); 
?>

Now, using this object, let's output the user's name:

<?php
	echo $user->{$prop->value}; // outputs 'john'
?>

Given the following class:

<?php
	class Employee
	{
		public $name;
		public $salary;
		public $position;
		
		public function __construct($name, $salary, $position)
		{
			$this->name = $name;
			$this->salary = $salary;
			$this->position = $position;
		}
	}
?>

Also given this class:

<?php
	class Data
	{
		public $prop1 = 'name';
		public $prop2 = 'salary';
		public $prop3 = 'position';
	}
?>

Output the properties of the Employee object through the Data object.