PHP Fatal error: Uncaught Error: Using $this when not in object context in file.php

<?php
class Foo {
	protected $_value;

	public function __construct(){

		return $this->_value = 1;
	}

	public static function getValue(){

		return $this->_value * 5;
	}
}

echo Foo::getValue();

As per php documentation,

Because static methods are callable without an instance of the object created, the pseudo-variable $this is not available inside methods declared as static.

https://www.php.net/manual/en/language.oop5.static.php

In the above code snippet, static method getValue() will throw the error this is the same use case.

Things to be noted in Static Method and Static Variable:

Static properties are accessed using the Scope Resolution Operator (::) and cannot be accessed through the object operator (->).

It’s possible to reference the class using a variable. The variable’s value cannot be a keyword (e.g. selfparent and static).