Reading a Non-Existent Property in OOP in PHP

Let's try to write data to a non-existent property - this will work:

<?php
	$test = new Test;
	
	$test->prop3 = 3; // write 3
	echo $test->prop3; // outputs 3
?>

Suppose we don't want to allow writing to non-existent properties. And, in general, we want to allow writing only to properties prop1 and prop2.

This is easy to do - it's enough to add the corresponding condition in the __set method:

<?php
	class Test
	{
		private $prop1;
		private $prop2;
		
		public function __set($property, $value)
		{
			// Let's write a condition:
			if ($property == 'prop1' or $property == 'prop2') {
				$this->$property = $value;
			}
		}
		
		public function __get($property)
		{
			return $this->$property;
		}
	}
?>

If there are many such properties, it's not very convenient to list them all in the condition.

Let's put the properties allowed for writing into an array and check for the presence of the property in this array using the in_array function:

<?php
	class Test
	{
		private $prop1;
		private $prop2;
		
		public function __set($property, $value)
		{
			$properties = ['prop1', 'prop2']; // allowed properties
			
			if (in_array($property, $properties)) {
				$this->$property = $value;
			}
		}
		
		public function __get($property)
		{
			return $this->$property;
		}
	}
?>